A secret document has revealed US government officials have so many programs of agents working undercover on social networking sites that they have had to create a coordination program.

The Electronic Frontier Foundation obtained the document under freedom of information laws. The document, “Obtaining and Using Evidence from Social Networking Sites” is authored by the Justice Department’s deputy chief for computer crime and a department trial attorney. According to the document, “social networking sites can provide evidence of personal communications, motives, personal relationships, bogus alibis and criminal enterprise.”

It also notes that these sites can often help agents find “instrumentalities or fruits of crime”: in other words, after pulling off a heist, it may be a bad idea to be pictured with a freshly acquired tan and gold chains.

Perhaps the most amusing element of the presentation is that the Facebook and Myspace profiles used to demonstrate the sites’ workings are those of Demi Moore and a contestant on America’s Next Top Model, suggesting office drones everywhere will always find a way to liven up routine tasks.

A separate document from the Internal Revenue Service notes that tax investigators are barred from creating false accounts to obtain information, a policy that doesn’t appear to apply with all government departments. The Associated Press notes that state and local police, the Secret Service and the FBI now co-ordinate their online activities to avoid compromising each other’s investigations.

Of course, it’s not just law enforcement officials who have to worry about the possibility that neither party in an online discussion may be who they claim to be, as shown in this sketch (the payoff to a running series) from dark comedy MonkeyDust: