If you’ve been up to “no good,” you might want to think twice about who you ‘friend’ on Facebook and other social media sites, because there just might be a government official trying to track you down. The EFF (Electronic Frontier Foundation) has been collecting information on how a variety of U.S. federal agencies are fighting crime using Facebook, MySpace, Twitter, LinkedIn, and other social networks.

The EFF, who have been collecting details on the social media tracking efforts of U.S. agencies, has published a justice department document [PDF, 35 pgs] that outlines how agents can use social media to track suspects and get them to reveal incriminating details. While a parallel IRS social media policy and training document [PDF, 38 pgs] indicates that agents are not allowed to obtain information via fake identities, other agencies such as the FBI, U.S. Marshals, the DEA, and BATF apparently don’t have such policies in place. In fact, FBI agents have apparently created fake identities to lure and track suspects. Cases are widespread as to reason for tracking, including sex offences, tax infractions, and other potential criminal activities.

This news kind of makes Facebook’s publishing of your consumer purchases pale in comparison, in the privacy violation spectrum. So if you’re concerned about your privacy — and hopefully not because of crimes you’re committing — make sure not to friend people you don’t know, especially those with no profile pic and no friends in common. Of course, if your friends confirm ‘add’ requests willy-nilly, strangers can still access some information about you through them. So learn all you can about Facebook privacy features and apply whatever is appropriate.