bogus contacts in outlook and hotmail

It does not happen very often, but I sometimes get bogus contacts in my Outlook address book.  They are coming from my Hotmail account since I have the Hotmail interface to Outlook.  I can delete them in Outlook and it somehow synchronizes the delete over in Hotmail.  But the really weird thing about it is that many of them have the word "camp" in their name.  In fact most of them.  Who are these "camp" people and how can I stop them from hijacking my contact list?  I have Windows Vista with all the updates.  Any information that you have would be greatly appreciated.