How costly or difficult would it be for an ebay software coder to prevent multiple account holders to bid on their own auctions? The coding already exists for any eBay user to block any other user. I think this could go a long way toward reducing shill bidding. Of course, the problem of a different user (a relative or friend) bidding would not be addressed.
I also am wondering if the winning bidder (not the shill) has any recourse in the courts against unscrupulous sellers? I would hope so.