Here's something that happened when I worked at eBay:
It's not uncommon for a person to bid some outrageous amount at the last second to ensure that they win. Good plan, eh? That is until somebody else gets the same idea and bids some outrageous amount on the same item.
Something like a $20 item ended with a winning bid of well over $2,000. Bid history revealed that two bids in rather large amounts were placed at the last second. The winner hurriedly wrote to support trying to weasel out of the deal... claiming an accident. Somewhat believeable accident, but not likely...
My favorite story:
I received a letter from somebody that was bidding on an item. The auction was ended early. He was threatening to sue eBay (something we got threatened with everyday). Upon review of the auction in question, I discovered that the seller had intentionally ended the auction early and sold to the high bidder. I wrote back a rather sarcastic letter... that may have had something to do with my getting fired.