Not all bids are live bids - soem are "shills". Either the seller himself, or an ally, bidding up the item. Also the same procedure can be used to pretend that an item is "no reserve", or already past a low reserve, in order to stimulate interest, yet provide the seller with the protection he would have if he set an honestly high reserve. Example: "looney01" is taking bids on a plasma TV, supposedly in a "no reserve" auction, but "couch_spud103" (actually himself or a confederate) will make sure that any bid LESS than $1800 is "over-bid", in order to prevent someone from winning it at a low price. Then if the shill buyer "couch_spud103" is the high bidder, "looney01" re-lists the same item the next week, possibly claiming "winning bidder never followed through". I was the "loser" outbid in the last minute on one such scam.
As to "sniping", it is flately unethical - in a real auction, there is an interval after a bid where the auctioneer solicits further bids, until it is plain there are no more.
How to fix it? Two simple steps...
1. Any bid in the last two minutes results in an automatic extension of the auction's close. In other words, to be the "high bid", it has to stand unchallenged for over two minutes - otherwise, more time is granted.
2. Require that any auction where the "winning bidder" fails to claim the item, it automatically goes to the next-highest bidder, if they still want it - and so on down the list of bidders.