Is there a seller that one doesn't have to watch closely for bid retractions, bidders with 90-100% of their history with the same seller, etc.? I watch for that on every auction.
I actually think its one of the positives of eBay that you have that visibility. I've dropped out of auctions where I was bidding against bidders that had a number less than 5 next to their user name (I'm not sure what the number is called). I've also spotted a case where the previous auction types the bidder had bid on were mostly apparel and other stuff. It was suspicious to me that person was suddenly bidding on 1930s football cards - eclectic taste I guess
And even though I snipe in the end, I usually throw a few bids out to get a feel who is bidding against me. And the final method I use is that if the item is already over my valuation on the last day which happens - I walk away - no reason to set a snipe in that case. Of course there are sellers I won't deal with - but I'm pretty lenient - the alternative - dealing with sellers where I feel there is 0% chance of an auction being tampered would be kind of boring and maybe impossible because of the nature of the system.