Hmmm...if what you mean is an all-out purge of the hard drive then that would mean starting over for everyone - including yourselves.
People can have as many as they want, although it is annoying when someone you've never seen before blindsides you with bad language etc. and you have no idea what they're talking about only to find out you really creamed them whilst they were under a different name.
But for now, I can't imagine all thse names are much of problem insofar as gameplay is concerned so rather than have to deal with some screwy system of submitting an online form asking to have certain names removed (the chance for error is pretty good there) or a clean sweep, it doesn't bother me.