[grey-area]

In the crude sense of collecting all your posts and sending them all to an advertiser, of course not. In the sense of selling your interests, friends, social position, age etc to advertisers as a datapoint, yes they do; that's how they target ads and make money. They also tried to harvest purchasing habits from other sites like Amazon (with Beacon), and give broad access to developers, some of whom abuse the privilege and have been caught selling data on. I'd expect that sort of activity to increase post-IPO. They're not alone in this of course - gmail does the same, without the data lock-in.

[Xuzz]

No, they do not sell interests to advertisers. What they do is allow advertisers to show their ads to people with those specific ages, interests, and such. It's a subtle and important difference: with this method, advertisers only know that their ads are being shown to someone who matches their criteria, not who. Advertisers are not able to correlate your identity with ad targeting.