Mathew Ingram notes that businesses are starting to worry about time lost to Facebook (et. al.):
The BBC has a story about a survey that says businesses are losing hundreds of millions of dollars a day because employees are wasting time on Facebook and other social networking sites. According to this consulting firm, 233 million hours worth of work time is lost every day -- and the firm recommends that more businesses ban or block Facebook, as both the Ontario government and Toronto City Hall have done recently.
Here's a small suggestion for managers who have this idea cross their mind: How about you try doing your job? If you have staff that isn't getting assigned tasks done, then perhaps it behooves you to notice that fact and do something about it? Banning access to websites (or even the web in general) is simply an abdication of responsibility on the part of management.