What makes Facebook worth $100 billion? (Likely somewhat less, as Suzanne Vranica and Shayndi Raice explain in The Wall Street Journal.)
Topping the list is the revenue-generating potential of the company's upcoming Premium ads and other new advertising programs.
Facebook, Google, and just about every other big-name Web service make their money by selling ads that get targeted based on what they know about you. The companies say they don't sell personally identifiable information to third parties, but one way or another, information about their users is the services' bread and butter.