I've never sold on eBay but I buy an enormous amount of items there. I can't give you a definitive answer to that question, but I can say I've been "shilled" a lot. You can click on the number of bids, then click on an individual's bid history and see how many times that bidder has bid with which seller, and see how many times that bidder has cancelled and/or withdrawn a bid. When one bidder has withdrawn over 80 bids in one month, it certainly makes you wonder why, and makes you wonder why eBay still allows that person to keep bidding. The bottom line is that shill bidding drives up the final price which benefits both the seller and eBay. So why should eBay care? I continue to buy on eBay simply because I can still find good deals there.