Have you ever wondered why Facebook spends so much time encouraging marketers to take advantage of its free Brand Pages? The effort seems counter-intuitive: It costs Facebook money to provide, maintain and serve Brand Pages, and the company gets no revenue from them.
http://www.businessinsider.com/this-diagram-shows-facebooks-plan-to-keep-advertisers-locked-in-for-years-2012-9
Toms Blog on Life and Livingness