Although traditional ascending price auctions use a "soft close" format - where bidding continues until a final bid is placed, the majority of today's on-line auction sites use the "hard close" format - also known as a ‘time interval" auction having a set time limit, regardless of ongoing bidding. It is important to note that in a "soft close" format, bid snipping, that is bidding during the last few seconds or minutes on an item, is eliminated since the auction stays open as long as bids are being made.
In an attempt to minimize bid snipping and provide more of a "soft close" characteristic to their "hard close" auctions, eBay allows bidders to use "proxy bidding". In proxy bidding, a bidder enters the highest price they are willing to pay for an item when they first bid. The bid begins at the lowest possible level and increases automatically only if their original lowest bid has been beaten.
From the buyers standpoint a "hard close" format is preferable since they may be able to make a final bid before others can react, possibly winning the auction at a lower price.