I snipe for two reasons. One is to take advantage of people's tendency to not figure out what their real high bid would be until someone puts in competitive bid. Since I could do the same thing if I had time to sit at my computer every time I want to bid on something, this seems competitive but not unfair.
What actually drove me to AuctionSniper, though, was being bothered by how often I won the item, but at my very top bid. I know it seems paranoid to think that somehow sellers were able to figure out my high bid and put in phony bids to make the sale at my high bid price. Some cases seemed obviously to involve phony bids (shills), although proving that is something else. Maybe I was only the victim of one of those random strings of events that look meaningful. I particularly noticed this problem when I would make bids at some odd number (like $101.37) and that turned out to be the winning price. Anyway, since I started using AuctionSnipe, ... no problemo. (Maybe I should see a psychiatrist and get some meds.)