You never know who is checking out your Facebook profile, reading your tweets, or looking at your MySpace messages. But if you broke the law or are under scrutiny from the feds, then the FBI may already be "following" your online activities on different social networking sites like Twitter, Facebook, MySpace, and LinkedIn. A new internal Justice Department document obtained by San Francisco-based civil liberties group, Electronic Frontier Foundation (EFF), details how federal agencies like the IRS and the FBI are now using social media to monitor suspects' online activities and also track down their whereabouts.