My understanding was...
If you bid a maximum amount of, say £50 on something then eBay will automatically bid on your behalf up to your maximum. Therefore if the current highest bid is £30, eBay will place a bid of £31 for you, making you the highest bidder. If someone else then bids £32, eBay will re-bid for you at £33, and so on up until the point where someone bids £51 and you have to increase your bid to stay in the running.

Auctionsniper etc on the other hand won't place *any* bid until two seconds (or however long you specify) before the end of the auction - therefore if the highest bid is £30 and you set the sniper to put in a £50 bid with two seconds remaining, you'll win the item for £31, since the other bidder hasn't got time to increase their bid, thus guaranteeing you the item.
(Professor Kenny Martin Hmm? What?, Sat 6 Oct 2012, 16:16, 2 replies)

This is correct.
And it's the way eBay have always worked AFAIK and I've been selling on there for 10 years or so.
( His Popiness the Hole Invaded Poland on, Sun 7 Oct 2012, 21:49, closed)

Well, yes - in this scenario, the person using AutoSniper (or whatever) would win the auction. THe fact of their using AutoSniper is, however, as irrelevant as Autosniper itself - they won because they bid more money, albeit somewhat late in the day. If the bloke with the original £30 winning bid had specified a maximum of 51 quid, he would have won it - again, on account of having bid more. AutoSniper brought nothing to the party but tardiness.
( Happy Phantom has been to Hastings, Brighton, and Eastbourne too, Sun 7 Oct 2012, 23:44, closed)

The point of sniping an auction though is that the other person doesn't have time to increase their bid
Because by the time they find out they've been outbid the auction has closed.

Your theory is correct, but only if people decide on a maximum amount and bid it, then leave the auction to run. Lots of people don't do that though, they bid a bit, get outbid and then bid again.
(Professor Kenny Martin Hmm? What?, Mon 8 Oct 2012, 16:49, closed)

I genuinely don't understand why people would do that, but I'll take your word for it - it certainly wouldn't be the stupidest thing I've seen. Still - presuming correct use of the features, it's the highest bid that wins it; the AutoSniper is no more able to extend past its upper limit than ebay's own inbuilt 'maximum bid', so the goods will go to whoever's maximum bid is highest, irrespective of when it was placed...
( Happy Phantom has been to Hastings, Brighton, and Eastbourne too, Mon 8 Oct 2012, 17:08, closed)

You're right
If Auctionsniper bids £50 with 2 seconds remaining, but someone previously bid £51, then you'll still lose the auction. They'll be very surprised though, when the bargain they were about to win for £22.67 suddenly more than doubles in value at the end :)
(Professor Kenny Martin Hmm? What?, Tue 9 Oct 2012, 10:09, closed)