An employer has no right to ask for a password, pin number, bank statement, medical documents or any other confidential information. If my boss, threatened to fire me if I didn't give up something confidential, I would remind my boss that threatening me is as good as a declaration of war, see you in court!
-Don't forget to air your bosses dirty laundry while you're at it. Especially since he is so interested in every one Else's.
What employers are trying to do on a daily basis is in my book, far more scandalous then the stuff they are trying to fire their employees for. I think they need to be reminded of this.
That being said, if your arrested, for something you did, I could hardly blame the company for filling the slot while your gone. Also, if you are publicly slandering a buisness you are employed by (public, not with your friends...) this is about as good as standing out front chucking bricks at the windows. Yup, terminated!