Facebook might be selling you out to the government.
With the help of the University of California Berkeley's Samuelson Clinic, the Electronic Frontier Foundation (EFF) filed a Freedom of Information Act (FOIA) request for documents from the government about how they monitor and use social networking sites like Facebook, MySpace, Twitter and LinkedIn to gather information for investigations. The EFF struck gold with this request, as both the IRS and the Department of Justice released training presentations on social networking sites. While this may seem benign, the training material from the DOJ suggests that feds go undercover on sites such as Facebook to gather information on crime.
The DOJ slide show presentation (pdf) also discusses how cooperative these social networking sites are in complying with requests for private data. For example, Facebook, a highly popular social networking site, was described as "often cooperative with emergency requests," while Twitter was less cooperative because they refused to preserve data without legal process.