All sniping does is hide the fact that there is an interested bidder out there - you are hoping that the current bidder doesn't have their maximum price in the proxy bid system and don't want to give them a chance to revise their bid.

If you do snipe, make sure you put a reasonable price in - I have seen a sniper pay $500 for a $100 item because the current bidder had a large proxy bid to deter snipers!

Gareth