Shill is someone who bids up an item with no intention of getting the item, only making the other bidder go higher. You see it at Auctions all the time. Some time during the night they put back up an item that had previously sold and give some verbage that the bidder was confused or found a slight flaw or his credit card was no good. All kinds of reasons, but most of the time it is when the seller got stuck with his own item.

...and that's my 2 bits worth