Can you get banned for using AS with U.S. eBay???

The best thing most of us do is:
Log into your "My Snipes"
Then click "modify account"
scroll down to near the bottom and where it says
"Insta mail" be sure to UN CHECK the Yes feature.
That way the seller has no way of knowing if you used AS or not. They can only wonder.

From eBay:

Is it permitted for another bidder to bid on an item I was bidding on at the very last second and win it?

Yes, it is.

Within the eBay Community, this practice is called "sniping" and it means to place a high bid in the closing seconds of an auction-style listing.

As frustrating as it can be to lose an item you really wanted, sniping is part of the eBay experience, and all bids placed before a listing ends are valid - even if they're placed only one second before the listing ends.

One way to help avoid disappointment is to ensure that the maximum bid you enter on the item page is the highest price that you're willing to pay. The eBay proxy bidding system automatically increases your bid up to the maximum price you specify, so entering a higher maximum may help prevent you from being outbid in the closing seconds of a listing.

eBay could find easily that the a biding was placed by a sniping service such as Auction Sniper, for example, by analysing the IP address of the connection.

If you are using sniping software running on your home computer this may be more difficult since your IP is not shared with many other bidders, but they can come up with other ways to distiguish bots from live browsers.

However, I think they are OK with automated sniping so I am using AS myself.

Zapta