One of the externs passed this along, dealing with the USPTO's rejection of someone's application to register "Obama Bin Laden" as a trademark. Among the reasons for the rejection was the failure to get written consent from Barak Obama and Osama Bin Laden. Don't miss the classy airbrush image.
Note that this doesn't mean the guy can't sell Obama Bin Laden merchandise. It just means he can't stop others from doing so (which is where the real money would have been).
I think the title of this post should be "You can't trademark everything (TM)."