I'm (thankfully) out of date on Facebook marketing tactics, but gating content behind Likes and Invited Friend Counts is standard - there are even plenty of sweepstakes to win just for consenting to being shown a like button. Generally speaking, the content behind these gates is a single payoff - a little nibble of digital content. Companies love that trade for ears to promote content to, "like" being a friendly euphemism for "subscribe" and all.

I'm sure it's been tried, but it might be interesting to check Like/Follow persistence in exchange for long-term access to content and services. "Have a twitter account following ours? You're in!"

I use the method on http://www.twitterdoctors.net/ and more than 70% of my followers are now doctors, which is useful for the occasions I do tweet about new features and stuff related to my healthcare start-up.

For those interested, I am in the process of re-writing the site (dev version at http://www.twitterdoctors.com/) – to automate the process, try the wizard out, it uses twitter's new event listeners.

Your site violates Twitter's trademark. You need a different name...

These guys have: http://everytimezone.com/ Awesome service, the only "ad" is for their other product, which is not free.

It seems like a kinder version of the tweet/like to download which is pretty popular for music marketers.