In April 2006, soon after Facebook started to gain some traction, recent Harvard graduate and maths genius, Jeff Hammerbacher joined the company in an attempt to help it gain deeper understanding of the site's attraction (or not) to various target groups.

Two years later, and entirely disillusioned by the experience, Hammerbacher departed Facebook, saying, "The best minds of my generation are thinking about how to make people click ads; that sucks."

And that is exactly the core of Facebook's business.  People clicking ads... and vendors paying Facebook for those clicks.

One of the first things that anyone using Facebook needs to know is that they are the product, not the customer.

Think about it.  What is it that generates income for Facebook?  Clearly it's advertising.  And with that in mind, clearly Facebook is selling to the advertisers.

What are they selling?  Nothing more than well-identified likely purchasers of the advertised product.  Thus the better Facebook can define its product (that would be you, the Facebook user) the more they can charge for the advertising.