I've had people enter wrong amounts and retract the bid, then bid again and win the auction.... although i think that mine was pretty geniune.... it sort of depends on how much they bid for the item....

I was selling a car part but it started at about 40 or 50 dollars... 

But the bidder (and eventually the buyer) bid 2 amounts and retracted both bids.... first bid was for $4050... second bid they put on was $8050.... in about 2 minutes of each other! 

The next day they retracted both bids and put what i'm guessing was a "normal" amount on it... 

I had to laugh over it... 

I nearly wanted to message them and tell them not to surf the net while drunk.... 

Other bidders though, do "test the water".... 

and some i think just have nothing better to do than make other people pay more than they should as they themselves cannot afford the item and are peeved over it....