New legislation introduced to Congress today seeks to prohibit employers from requiring employees to provide access to personal email accounts, social networking profiles, and other private data as a condition of employment. Introduced by a team of democrats led by Senator Richard Blumenthal, the Password Protection Act would institute financial penalties for employers that discriminate against current or prospective employees who refuse to offer up personal login information. The legislation would not, however, prohibit employers from setting usage policies for company-issued computers. http://www.theverge.com/2012/5/10/3010826/password-protection-act-prohibit-employers-facebook-access
I think they may have felt pressured from Facebook though, as Facebook threatened to sue any employer doing this; it's against Facebooks TOS to give access of your account to 3rd parties (not including apps)