The Information Commissioner's Office has sent out a warning to employers in the UK, claiming it would have "very serious concerns" if they were to ask their existing or would-be employees for Facebook login credentials.
"The UK Data Protection Act clearly says that organisations shouldn't hold excessive information about individuals, and it's questionable why they would need that information in the first place." A spokesperson for the ICO has commented. This follows an Associated Press report in the US exposing the practice of employers asking for Facebook passwords during job interviews, and whether this is in violation of federal law.
Details on a Facebook profile (gender, race, age, religion, etc) are all protected from being used to determine the employability of a person, which would put the employer vulnerable to charges of discrimination if they don't choose to employ that person.
While the legalities of the situation are very much a grey area in America, employers in the UK would be very much in breach of the Data Protection act, as it constitutes "excessive" information about an individual.