I wouldn't call myself an eBay pro by any means, but I was a power seller for two years. Unless things have changed much since I stopped selling on there a year ago, sellers with a standard set-up know how many are watching the auction, but they don't know who the watchers are. If you've added an item to your 'watched' list, it would show up on your 'My eBay' page anyway and you wouldn't have to keep re-visiting the listing to see the high bid.
Many use a third party program called Sellathon, and by means of a piece of code inserted in their listings, can tell if an item has a snipe on it, but not who's sniping (unless you turn out to be the only bidder on the item, in which case they'll obviously know it's you that was doing the sniping).
I seem to remember that IP addresses were a function of Sellathon too, and that sellers with an eBay shop had access to similar software with progressively more features according to the level of shop they had. I don't remember it showing snipes though. Whatever the stats package the seller happens to be using, they're pretty much all designed to show the volume of visits/level of interest in the item and the geographical regions that the interest has come from, but none invade the privacy of the individual user.
My experience with eBay was very much like the one you reported having earlier with Google (forgive me if I've got that wrong and that wasn't you) and so Mother Nature has kindly let me forget a lot of it in the same way she lets us forget the worst of childbirth
Still, I hope that was of *some* help to you.