Facebook chief privacy officer Erin Egan writes:
In recent months, we’ve seen a distressing increase in reports of employers or others seeking to gain inappropriate access to people’s Facebook profiles or private information. This practice undermines the privacy expectations and the security of both the user and the user’s friends. It also potentially exposes the employer who seeks this access to unanticipated legal liability.
If you are a Facebook user, you should never have to share your password, let anyone access your account, or do anything that might jeopardize the security of your account or violate the privacy of your friends.