Fed legislation is moving slowly so some States have gone ahead making it illegal
http://news.cnet.com/8301-1023_3-57561743-93/six-states-outlaw-employer-snooping-on-facebook/
http://news.cnet.com/8301-1023_3-57561743-93/six-states-outlaw-employer-snooping-on-facebook/
They can really ask for your FB password???