Apologies for some duplication of the reply above, which was posted while I was writing virtually the same thing....
I agree that bid snipers are a very valuable tool, as it completely removes the emotional aspect of an open auction.
It is well known that if an existing bidder is outbid and has time to rethink their position, they will very often increase their maximum bid higher than before to avoid being 'outdone'. It is just human psychology.
Even if every bidder used a bid sniper, it essentially changes the open auction into a 'sealed bids' auction, but instead of paying your maximum bid (as would be the case in a sealed bid auction), you just pay the next bid increment above the next lowest bidder.
You also have the facility to group items that you want to purchase, so that it just keeps bidding on similar items for you until it wins one of them and then stops. Set it and forget it.