Every time you bid and theres a change to your bid then MLB notifies you with an email. When I checked a previous email after some time where this individual ran me up then I could see he had changed his name. I guess once you change your bidder name it even updates in past history.
I'm new to this site so I don't want to start naming names right off the bat because I'm not even sure that would be appropriate but I will say it happened while bidding on Red Sox items. Only once did I have a problem with him but I've seen him do it to a number of people.