Facebook is one of way, waaay too many companies doing the datastalking thing. But heck, they're not even among the worst (yet). Check out:
The Wall Street Journal: "What They Know"
"Marketers are spying on Internet users -- observing and remembering people's clicks, and building and selling detailed dossiers of their activities and interests. The Wall Street Journal's What They Know series documents the new, cutting-edge uses of this Internet-tracking technology. ..." Source [blogs.wsj.com
(After seeing their detailed info, this habitual user of dictionary.com (dictionary.reference.com) will never go there again.)