Australian employers seem to be facing a dilemma, block Facebook and Myspace and possibly lose out on up to 50% of employee pool - or don't block the social networking sites and just put up with employees frittering time away on them. From Scopical:
"In the Deacons Social Networking Survey 2008, almost half of those who used social networking sites at work said that if given a choice between two jobs equal in all other respects, they would choose an employer which allowed access to these sites over one which did not". Link