I did some business with a ad salesmen from Facebook in my not too recent past. Make no mistake about it, they want to know everything about you. Your favorite movie, what political conversations push your buttons, when you want to get married, whether or not you shave your armpits. Every aspect of your personal life is valuable to them from an advertising perspective, and they will go to any length to get a hold of that information. A big part of what Facebook will be doing in the next 2-3 years is finding new ways to gain access to you. That's really what their major acquisitions over the past few years have been about. That's why they want yahoo. Facebook wants to be the defining mode of communication for every living human, and has some perverse incentives for doing so.