I agree that there could be harm to sellers' winning bids if everyone were sniping and there were no bidding wars. However, a sniper can only win if they bid more than the existing bids (sometimes after a bidding war).
I can say from experience that I was pleased when I saw that a buyer had sniped my auction. I had looked at it about an hour prior to closing and was pleasantly surprised when I saw that my price had gone even higher.
I guess I don't understand the objection for a seller unless he is also a buyer who only believes in "manual sniping" or is bitter that he can't win any auctions. In which case, if you can't beat 'em, join 'em--he can do the same thing.
The idea of manual being somehow better than automatic seems to beg the question of the whole e-Bay system. I mean if you want a manual auction, get in your car and go to one on the weekend. Then you can "manually" wave your number in the air and everything....