Whether it's shilling or not, it's an awful trend that Ebay doesn't seem to give a crap about.
There are hundreds of bidders out there now who are using bid retractions just because they can or as a bidding strategy. Either out of curiosity to see how high an auction is bid up to, before they retract their bid, to interfere with an auction for their own benefit, or to interfere with an auction, just for laughs.
I even got an angry e-mail from one of these guys after he retracted a bid in one of my auctions with just a couple of days left. I went and checked his history, saw he had a ton of retractions, and then I blocked him from my auctions.
"Why did you block me from your auctions, I have perfect feedback?" I hear back from him.
I explain to him, he's making me look like a shiller by retracting bids, and then trying to bid again, and that he has a regular history of doing this, so I can't really trust him. He gets back to me........."Oh, I had no idea, I promise I won't do it again."
Limit bid retractions, problem solved on many levels, Ebay..........nah, they have no scruples.