I've seen some people use Facebook ads to a free webinar or video opt-in, other leverage their Fanpage and do promoted posts to other in-FB landing pages, etc. Just curious what you've seen work great, and the kind of numbers you've been able to get re-cost per email lead (double opt-in).
I use the FB Login App to collect FB Verified leads thru an App on my Fan Page.
See this video which explains http://youtu.be/5tjVNf9H_Uk.
I have mainly offered a free software trial - 7 day ecourse, or registrations for live hangout events which I also host on my Fan Page.
It has been very effective, generating over 40,000 leads in the last 15 months for one of my businesses. The best part is that 90% of the traffic is a result to a high viral coefficient.