Facebook has issued a warning to employers not to demand to see the Facebook page or obtain the Facebook login of potential job applicants. In fact they have threatened legal action against any company that does so. They say it is a violation against their policy of not sharing passwords.
There have been several reported cases of job applicants who have been asked during an interview to either log on to their Facebook page on the spot or turn over their login credentials so the company can review their page for any potential wrong doings that may affect their job performance if they were hired. One applicant he was told he needed to tell the employer his Facebook password so they could log in to prove he had no gang affiliations.
Facebook's chief privacy of policy officer said that if an employer finds out that a job applicant is a member of a protected group and are asked to show their Facebook page, the employer may be in for a claim of discrimination if they don't hire that person. Even the American Civil Liberties Union spoke out against the practice.
Its a general rule of online behavior never to share your passwords with anyone unless you want to risk getting yourself into trouble for something they do since you may be held liable for it even if you didn't do it.