Update 2/22, 5:11pm: The Maryland Department of Public Safety and Correctional Services has suspended the practice of asking for Facebook login information for 45 days, according to an email they sent to The Atlantic. See our full story on the development.
The American Civil Liberties Union has taken up the cause of a Maryland man who was forced to cough up his Facebook password during a job interview with the Department of Corrections in that state.
According to an ACLU letter sent to the Maryland Department of Corrections, the organization requires that new applicants and those applying for recertifications give the government "their social media account usernames and personal passwords for use in employee background checks."
The ACLU calls this policy "a frightening and illegal invasion of privacy" and I can't say that I disagree. Keep in mind that this isn't looking at what you've posted to a public Twitter account; the government agency here could look through private Facebook messages, which seems a lot like reading through your mail, paper or digital.
While it's not surprising that some employers might want to snoop in your social media life, it strikes me as a remarkable misapprehension of what Facebook is to think that it should be wholly open for background investigations. Legally, things are probably more complex, but it seems commonsensical that carte blanche access to your communications should be off-limits.