why people snipe on eBay

So, the question is, when is sniping worth the risk of not getting your bid in? There are lots of reasons it might be. The easiest case to think about is of a bidder who has some expert information about the item being sold, information that might affect how much other buyers are willing to pay. For example, suppose that a dealer in Persian carpets sees a desirable one on eBay. Many bidders may not be able to tell the difference between valuable carpets and cheap imitations, and so if they can identify that a dealer is bidding on a particular carpet, that will tell them that it is a good one. So, the dealer can try to conceal who he is, to avoid starting a price war, but for a dealer who bids a lot, it is hard to have lots of different usernames. A simpler strategy is for him to snipe, so that others can't piggyback on his expertise. But even without special expertise, a bidder may feel that an early bid will inspire others to raise their bids, and in such a case, sniping may be a winning strategy.

They also have some other interesting articles (I didn't notice at first that it was a Harvard Business School site).