Maryland's signed into law by Gov. Martin O'Malley in May, for instance, was prompted by an incident involving a state Division of Corrections worker who was asked to provide his Facebook login credentials during a recertification interview.

The incident drew considerable criticism from the local chapter of the American Civil Liberties Union (ACLU), which called it a violation of the worker's First Amendment rights to free speech

In a earlier this year, the Council of State Governments (CSG) recounted another incident in which an elementary school teacher's aide in Michigan was suspended, and then fired, for refusing to provide access to her Facebook account. That request came after a parent reported seeing an inappropriate photo of hers on Facebook.

The teacher has sued the school district for wrongful termination.

"People have been asked to delete their social media accounts, 'friend' a human resources director or coach, or even hand over the username and password of a personal account," the CSG report said. "The latter could mean the employer or school administrator could view very personal information about the individual in question, including, for example, his or her history of Facebook messages."