Facebook is warning employers not to demand the passwords of job applicants, saying that it's an invasion of privacy that opens companies to legal liabilities. The social networking company is also threatening legal action against those who violate its long-standing policy against sharing passwords. There were reports this week of cases of job applicants who are being asked, at the interview table, to reveal their Facebook passwords so their prospective employers can check their backgrounds. In a post on Friday, Facebook's chief privacy of policy officer cautioned that if an employer discovers that a job applicant is a member of a protected group, the employer may open itself up to claims of discrimination if it doesn't hire that person.Not sharing passwords is a basic tenet of online conduct. Aside from the privacy concerns, Facebook considers the practice a security risk. Facebook spokesman Andrew Noyes said that the company doesn't think employers should be asking applicants for their passwords because “we don't think it's the right thing to do.”