I haven't noticed much discussion on this post from OUT-LAW.com (which is run by law firm Pinsent Masons).

The assertion is that - in some very precise circumstances - employers could own their employees' profiles or other data created on social networking sites like Facebook, Bebo, etc. I'm sure legally speaking they are right, although it'd be a nightmare for any company to get dragged into.

It cuts both ways too. I suspect many employers are more worried about accepting any liability for their employees behaviour on, or through, social networking sites.

Either way, its another chapter for the Staff Handbook.