I have designed a few of these online marketplaces and I can tell you from experience that in this day and age, phone numbers are a deterrent on a signup form. I advise against it and agree more with the cons.

However, that does not mean that you cannot get feedback from students. Form the past websites that I have built with student demographics, I have found that they like to interact with each other, so a better way to get feedback is to set up a forum in your online marketplace. Also, just adding a comment thread like blogs have is a very good way to get feedback, even more effective than phone numbers.

Also, one reliable method that I found works is an incentive based feedback survey when students can earn pennies on the dollar to take surveys. If you go this route, you could offer 25 cents or $1 or even $5 to the first 20 or 100 students that fill out the survey answering all your questions that you would normally have asked over the phone.

I hope my suggestions are helpful to you. I can always assist you in building your online marketplace. I have more suggestions for you as well.

Bruce

If these are paid students, you should. Not only you can get feedback, but you can TEXT. Email is not always reliable.

Just have a line below the phone number field saying:

(Don't worry, we won't call you. The phone number is just for emergency only. i.e. you lose access to your email account or forget your password)

Unfortunately, I have to agree with Shams Juma on his answer of "it depends". However, there are a few pieces of information you should also consider while making an informed decision about a phone number field.

First and foremost always remember user intent when considering fields to add or remove in any form scenario. If any user, regardless of age or any other pertinent demographic information, suspects that giving their phone number will cause an unwanted phone call after the application process is over, there may be some reluctance on the users part to provide that information. It's a classic case of negative cognitive bias that can produce immediate anxiety with just about any set of users (just as you mention in your question as a "con").

The next question is, how critical is the phone number in terms of completing the application process? I just wrote an article about form optimization and one thing I stressed with consistency is being hyper critical of any fields that are considered to be optional and/or not required. One area I've found success is putting additional or non required fields directly in plain view on the thank you page. This can reduce friction amongst any user persona and giving them the chance, IF INTERESTED, to allow you to contact them after the process is complete. You can also choose to incentivize them to help participate as another answer mentions above on the thank you page without interfering in the application process. One thing that's consistent about most user groups (and there aren't many consistencies) is that most people aren't thinking about giving you feedback during any part of their customer journey. More than likely it's one of the farthest things on their mind.

Researching the combined psychographic and demographic data sets is important to identify "potential" friction and anxiety points, but don't get too wrapped up in it. You can use it as a baseline for your hypothesis, but I have seen hundreds of cases where extrinsic factors completely override any buyer modalities or personas or whatever you want to call them. Also, they can be counter productive to an agile marketing solution and the ability to move quickly to rule out what works and what doesn't. It's usually very beneficial as an ongoing documented process when you start to understand your user better and establish a baseline control that you will continue to test against.

The best thing about this entire process is, it's a continual test to find out what works. If you are debating on whether or not to put the phone number field in, try it, test it (and I will explain how here in a second) and figure out if it worked or not. Worst case scenario is you know what "NOT" to do going forward. In the world of conversion optimization and user experience, best practices are a thing of the past. In fact, worst thing you can do is to listen to a bunch of "experts" spout out best practices. If anyone gives advice regarding "best practices" completely ignore it as they have no clue to what they are saying.

Once you decide to include it in your first round of testing, make sure you have realtime inline validation on all your fields, as well as a link below or to the side (again test placement as well) setting an expectation on why you are asking for a phone number, just like another answer mentioned previously.

If you have the traffic and you can segment your users, by all means setup an A/B test. Most people assume that most sites have enough traffic and conversion data to do so, which is also rarely the case. If you don't have enough traffic, use a qualitative approach and setup a tool that records user visits like HotJar for viewing. It's about as easy as they come to install and it's very affordable. You can also set it up to only record the page that the form is on, so you maximize your time to just looking at videos where users are on the page where your form exists. There are other behavioral filters you can implement with HotJar in order to save time when reviewing videos as well. If you really want to get crazy combine HotJar and Formisimo together and you may very well get enough quan/qual data in order to feel comfortable with your decision. This is something I would definitely try before going down the A/B testing route especially if there is any doubt about having enough traffic to gain the right sample size.

Let me know if there is anything else I can help you answer. Good luck and would also love to know how it turns out. Thanks.

Jeremy

It depends. If your target audience doesn't require too much trust and they are willing to provide that information up front, then yes, ask for a phone number. To find out for sure, do one of the following two things:

*Get 100 (good sample size) sign-ups with email only and conduct a survey. In your survey, ask your audience if they would be willing to provide a phone number during their sign-ups. This way, you'll get it directly from the horse's mouth.

*Conduct a variant A/B testing. Ask for a phone number in your test group and see what the response rate is. The higher the response rate, the better the chances you can get the phone number.

So, start with the objective and work backwards by implementing one of the two aforementioned tactics.

I agree with Dan "The Man" Lok and I'll go a little further. While you'll want to keep your onboarding as simple as possible and eliminate any barrier to capturing that email... don't YOU make the decision for them. Rather, let it be OPTIONAL. Let them decide! However, I do suggest inspiring their trust and giving them some incentive to share it. Ditto to what Dan said, i.e. let them know you won't be spamming them or sharing their number and that primarily, it will allow them easy access to resetting password, etc. BUT also firstly, incentivize them to share their number by letting them know that occasionally you'll run special VIP first-come, first-served promotions via SMS and you'd hate for them to miss out! I'd also like to suggest that you don't get all crazy with psychographic insights, etc. It's easy enough to read up on good UX versus bad UX (check out useronboard.com for some cool teardowns and more). As a strategist, I'm very keen on insights, but we all know why folks don't want to share their phone numbers -- think about why you might not want to share yours and address that "psychological" barrier in the most succinct way possible. We also know that mobile marketing includes SMS/Text Message Marketing and there are plenty of fabulous stats available proving why you'll want to capture mobile numbers if you can. Let us know how it goes!
P.S. run some A/B Testing - tinker with your copy and design and see how that works too!

Here is the answer. No, do not ever ask for a person's phone number unless you have given them something that is really worth them giving you their phone number. For example, if you are a Bails Bondsman and you are helping someone to get out of jail, by all means ask for their phone number.

Other than this, you will scare almost everybody off by asking them for their phone number. In fact, most sites are only asking for email addresses and not eve first names now. This is leads to a non-threatening offer or environment.

I am adding information below that I have shared with others.
If you were looking for a doctor, you would go to a hospital. If you were fishing you might use worms even if worms disgusted you. You would not use ice cream to catch a fish for obvious reasons. Understanding this is the key to marketing. And understanding marketing is the key to get whatever you want in life or business.
For investors, try contacting owners of existing similar companies. They have more money and experience than you. Have them sign an NDA when possible before discussing your business proposition.
At the risk of sounding like a broken record, you really have a marketing problem. You have to position your company and pitch to reveal the hidden benefits of acquiring your products or even your company. It will not be easy, but it can be done. Then you have to show the potential clients that they are really just buying tons of money at a discount. For the marketing problem, follow my advice below or get someone who knows how.
So, here are several of my marketing solutions:
Bonus:
Here is $10,000 worth of information for free and in a nutshell. (each of these proven concepts could actually be worth millions of dollars in the right hands.
I like your idea. As a matter of fact, I will go so far as say, it is a great idea. So...don't give up. But don't keep beating your head against the wall either. You have to get over the wall.
You have to quit focusing on marketing and sales tactics and focus on a strategy. How do you to this? You have to come up with a really solid USP. Why would a customer choose you over others similar companies? Find the answer to this before you continue with your marketing strategy.
Secondly, you need an irresistible offer.
Thirdly, you need to give an unbelievable guarantee. By doing this and following the directions below on pre-launch and launch you should be a lot closer to getting real solid customers.
I didn't come close to inventing the pre-launch or the launch. Concert goers are very familiar with winning concert tickets by calling into radio stations or winning vip treatment, or back stage passes, lunch with a star, the list goes on.
Likewise, if you look at "professional wrestling," the whole fitting before the fight is just a pre-launch. PT Barnum was doing this for circus goers over 100 years earlier. And I can only imagine the pre-launch of the Romans for the Gladiator Fights.
In more recent history, every type of business from Retail Stores to Real Estate companies have used multiple pre-launch techniques. Believe me, tourists are bombarded with Condo deals when they visit Disney Land.
This is similar, but different from lead generation (I don't have the enough space to discuss this powerful technique here). But I use both of these techniques in my own businesses including offering a free information packed newsletter and encouraging my clients to move up my sales latter because it is best for them. Most do move up the sales latter as their ambition and drive increases. Some move all the way up from the very beginning. Both benefit from this, one just takes longer to receive the benefits. Others will never take a chance on becoming successful.
Okay, more to your pre-launch campaign for SaaS. Simply, come up with a taste of what you have, ask a serious question and answer it. At the end of the end of the first "answer and solution" set the potential client up with another problem that is very familiar to them. Tell them that you have the answer. Follow this technique several time. I believe most do this repetition 2 or 3 times, but a famous golfer has sent me literally dozens of how to videos in order for me to take the bait.
You might think that giving the answer to a solution makes your product less valuable and your opinion less valuable. If you think that, you would be wrong. Heck, look at what I have given out in this answer. My experience is if you give you will receive. That is if you know what to give, how much to give, and how to receive.
I am not trying to sell you on calling me. Most people frankly cannot afford it. Really, I am pretty busy with my businesses and consulting. However, I need more info before I could have a greater impact in helping you.
Most solutions involved this: Ask, Ask, Ask, then Ask again.
Concentrate on the 3 M's. There are actually 7, but 3 will do for now. These are Market, Message, and Media. They come in that order.
Who is your target market (customer, clients, buyers, users, etc.)?
Tailor your laser focused message for this target market.
What is the best media mix to get your message to that market?
Here's what you do...first, make it an offer that is so incredible that they cannot resist. Secondly, do all the work for them. Make it so easy to make the purchase now that they can do it virtually without effort. Thirdly, give them an incentive to act right now. Fourthly, offer an almost unbelievable guarantee. Fifth, offer a bonus for acting now. There are many other incredible steps, but these steps should help the novice to the professional sell anything.
Whether you are selling B2B or B2C, you have to focus on selling to only one person. You can actually sell to one person at a time while selling to millions at a time. They are one and the same. Don't get off track, what we call digital marketing selling is just selling in print. And that has not changed since Cluade Hopkins wrote "Scientific Advertising." Really long before he wrote the book.
The secret to success: I have had the pleasure of knowing and working with some of the biggest names in business, celebrities, actors, entrepreneurs, business people, and companies from startup to billion dollar operations. The number one reason for their success is doing what they know and love while doing it in new, creative, and innovative ways.
Ask, Ask, Ask. Have thick skin and learn from each "mistake." In a short while, the market will tell you what you need to do and who and what you need to ask. But get started now even if that just means asking a contact on LinkedIn.
While you are thinking, think big and think of something at least 1% better, newer, or different. And being cheaper is not a winning strategy.
Make decisions quickly and change decisions slowly..unless you are actually going off a cliff.
Remember these two 11 letter words...persistence and consistency. They are two of the most important tools ever invented.
Even better yet, remember my 411 Rule of Achievement – It consists of (4) eleven letter words for super achievement (also an 11 letter word). Here it is, my 411 Rule of Super Achievement:
Persistence and
Consistency can change even the smallest
Possibility into a big time
Probability
Persistence + Consistency =
Possibility  Probability
By the way, I get a lot of people asking me if I can take phone calls for free (a free sample). Sorry, I can’t. I respect Clarity.fm and what they are trying to accomplish.
Treat everybody you talk to and everybody you meet (including yourself) like each is your number one million dollar customer.
Remember this for most people who really want to achieve a dream:
First: Your dreams are important and those who don’t support and believe in your dreams either don’t understand your desire and ambition or they have some other reason (many times reasons they themselves don’t understand) for not wanting you to spend the time and effort necessary to achieve your dreams.
Secondly: If you haven’t achieved your dreams and goals so far, it is not your fault. I know that this goes against what you usually hear, but it is true. Stop blaming yourself. You have a whole world of obstacles that are truly the blame. You only need to figure out how to go over, go under, go through, go around, or go with these obstacles in the direction of your dreams.
Thirdly: Fear is normal, but don’t give into it. Use it to motivate you and guide you.
Fourth: You are right; there are probably some people who don’t want you to succeed.
Fifth: Keep this in mind, there are people competing to get their first, do more, have more, invent what you are considering inventing, or simply trying to win. Believing in yourself and what you are doing is part of a strong recipe for winning over your competition.
I also always suggest that everybody at every stage work with a coach, mentor, or consultant. Heck, it works for Tiger Woods, every team in the NFL, the NBA, and etc. We all need guidance and support.
Best of luck,
Take massive action and never give up.
Michael
Michael Irvin, MBA, RN
www.michaelvonirvin.com
PS – Many people have “Upvoted” my answers. Thanks to those who do this. I really appreciated.