A ComputerWorld article reports on a study that says social networking sites like Facebook are "leaking" personal information that allow third parties to tie Web browsing habits to specific individuals. The study looked at 12 different social networking sites and was able to determine that 11 of them were intentionally or unintentionally making it possible for third parties to tie your viewing habits to you personally.
Cookies and HTTP referrer information were identified as part of the problem. The report concluded that it was difficult for users of social network sites to counter this. A partial solution is to delete all cookies every time you quit your browser, which few people do. Cookies are heavily used to simplify logon to sites that users visit frequently, and regular cookie deletion will eliminate that convenience.