The way some internet auctions work is that if there is a bid within say the last 5 minutes the auction is extended five minutes and this keeps happening, it is not that the seller has the option to extend the auction the idea is that the gavel isn't banged until no more bids are made.

I wouldn't object to this style of auction if Ebay used it, however I'm sure some people would, this style of bidding creates a problem for people who don't have the discipline to stop at their own limit.