dtgreene: If you expect prospective employees to have Facebook accounts, you are discriminating against people whose real names and legal names don't match. Also, why should somebody's out of work activities have any bearing on whether the person is qualified for the job?
sasuke12: Would you ever hire a secretary who has a history of violence and getting in and out of jail ?
Would you ever hire a woman who has falsely accused innocent men of rape/violence ?
Would you ever hire a man who is a convicted felon and a pedophile ?
Sure it is an out of work activity but every human I ever came across ends up mixing work with private life.
Hiring damaged people is like playing with fire. Eventually you get burned.
There is a reason why you can't become a police officer, politician, president if you have drink and driving charges or prior criminal record.
Facebook is a great source of information.
Facebook is also a source of bad information. Somebody else might have the same Facebook name as the potential candidate, for example.
Also, there are other privacy issues: What if you find out something about the candidate that you are not allowed to use as a factor in hiring? (This includes Religion and, in some areas, sexual orientation and gender identity.) Even where it is legal, I consider it highly immoral to spy on the employer and, for example, deny employment because she happens to be transgender.
Also, you *can* become a politician with a criminal record, especially if the "crime" is something that is rather popular or is covered up. In fact, I suspect that politicians on average commit crimes more often than the average person. I can think of two cases where elected US officials have ignored court orders: One is, of course, Kim Davis for refusing to issue marriage license, while the other, much older (and much serious) case is Andrew Jackson (then the US president) ignoring the US Supreme Court and forcing Native Americans to leave their lands, causing deaths of thousands.