I think its something to do with eBay and Mellow Mike's way of listing, so that the privacy of the buy is protected.
eBay is doing that on the majority of listings with high bids now. I think it depends on the category, but it seems that once the bid hits $200, they hide the bidders ID's due to observers contacting bidders fraudulently. You can usually still see who won after the auction is over, but you can't see the other bidders. Basically it is just to protect the privacy of the losing bidders so they don't get emails from other people with the "I saw you were outbid, and I have one of those I could sell ya" spiel.