"Law of Auction" is, you offer the goods at auction, you must accept a high bid made in apparent good faith. You can be sued if you do not (although the chance of that is very slim). If a seller does not wish to sell to someone with Zero feedback, they should say that in their auction listing. However, a deadbeat buyer can always bid under an alias name (a friend's), so the feedback number is not really the deciding factor. Yes, with a deadbeat buyer, and the ensuing delay in opening and closing an eBay case, you might lose your second-highest bidder, or all bidders. That's just part of the excitement of the auction!