Thinking of traditional country auctions where Widow Dillmore's furniture and farm machinery are auctioned off to the chant of The Auctioneer...

How do they handle sales that fail because the winning bidder walks away without paying up? Do prospective bidders have to put up cash on the barrel in escrow before they can bid? Or does "negative feedback" for the defaulter involve taking him out behind the barn and beating the snot out of him? What would Sotheby's do?