A barrier requiring a user to "Like" a brand’s page before they can access certain content from that brand on Facebook.
Like-gating is an attempt by brands on Facebook to increase their Fans more quickly than they would otherwise.
The concept is nothing new. Simply replace the words "Facebook fans" and "social media marketing" with "email subscribers" and "permission marketing" instead. Some people will stay just long enough to take advantage of the immediate offer. Other people will stick around and be exposed to more messaging than if subscribing was optional. Like most marketing methods, you can try and determine the overall effectiveness with testing and analysis.
Like-Gating Works, Brands Doubling Up on Facebook
ClickZ (July 13, 2011)
What’s So Bad About Like-Gating?
Sysomos (March 25, 2011)
Please Like Us! (Are All Those Facebook ‘Likes’ Worth It?)
MarketingProfs (March 22, 2011)
Want This Facebook Offer? Better ‘Like’ Us First
ClickZ (January 31, 2011)