“Friending” co-workers depends on your level of organizational risk tolerance:
http://www.ohioemployerlawblog.com/2012/01/friending-co-workers-depends-on-your.html
See also Latest stats about supervisors being “Facebook friends” with employees reveals interesting generational data:
http://www.ohioemployerlawblog.com/2012/02/latest-stats-about-supervisors-being.html