You should read my other message : Not wanting to
sell an item anymore is one of the reason _explicitly_
listed on ebay as example to end an auction earlier.
The explicitly say that you first have to cancel bids
and then you can stop the auction. (canceling bids first
seems to have to be done so that bidders will get a
message from the seller saying why he does it).

Cheers,
Yann Stettler