Sniping does a number of things. People often complain that they are being "shadowed" by another user. This is using ebay search feature to follow what a person is bidding on. Rather than finding a cool item on their own, they let someone else do the work. Sniping prevents this by not giving the shadowers a chance. Sniping also stops "nibblers" . If you place your max bid on ebay long before the end, there usually are people that keep placing bids until they A) can't pay any more $$ or B) beat the person by one increment. This raises the cost of the item for you. If you snipe, the nibblers don't get a chance.