Federal investigators are lucky that a judge rejected U.S. Attorney Thomas O'Brien's claim that violating a website's terms of service constitutes unauthorized computer access under the Computer Fraud and Abuse Act. According to O'Brien's theory, which the L.A.-based prosecutor used to pursue charges against a Missouri woman for her involvement in a MySpace prank that seems to have precipitated a girl's suicide, investigators who disguise their identities or otherwise provide false information while searching for evidence at social networking sites are committing federal crimes. A.P. reports that such online trickery is common, citing a recently released Justice Department document that "describes the value of Facebook, Twitter, MySpace, LinkedIn and other services to government investigators." Some of the investigative techniques, such as checking fugitives' Facebook pages for clues to their whereabouts, seem unobjectionable. Others, such as impersonating friends or relatives to obtain evidence, are more problematic. When the trolling involves otherwise confidential communications stored by website operators or ISPs, federal law requires investigators to obtain a warrant.
Clarification: I was highly critical of O'Brien's grandstanding, law-twisting prosecution, which threatened due process by pushing an interpretation of the statute that would make almost every Internet user a potential criminal. I am not advocating federal prosecution of people who violate websites' terms of service, even if they happen to work for the federal government.
[Thanks to Tricky Vic for the tip.]