Jim, it seems to me that ethics ought to come into play more in this discussion. If the buyer was willing to pay $20 for the item, and shill bidding helped raise the bidding to $20, both parties are probably happy. But if in the course of that bidding some bids were placed by people who had absolutely no intention of paying for the item, that's unethical.

By the way, in reference to Steve Snowden's earlier post about the difference between an auction and a store, Yahoo's auction site has an interesting feature. Sellers have the option of listing a "buy price" - a price that automatically stops the auction and awards the item to the bidder at that price. That in effect gives the seller the option of turning the auction into a store.