I've heard it said that most bidders bid for a bargain and hope to win, whereas snipers bid to win and hope for a bargain.
The bottom line is that whoever has the maximum bid in place when the auction closes will win.
Sniping means not revealing your intentions to potential competitors while they have a chance of responding. This reduces the chances of bidding wars. To me, it seems that not sniping is just asking to be outbid.