- Shill bidding, which involves bidding on your own item in a deliberate attempt to artificially drive up its price. A shill bid can involve the use of secondary eBay registrations, user aliases, family members, friends, or associates to pump up the price; other bidders then have to top a higher price to stay in the game.
- Bid shielding, which is the practice of using shill bidding (but not a shill associated with the seller) to artificially increase the price of an item temporarily, in an attempt to protect the low bid level of a third bidder. Essentially, the artificially high bid scares off other bidders, and then the shill retracts the super-high bid at the last moment, leaving the bidding wide open for the initial, lower bidder.
- Bid siphoning, which happens when a third party (unrelated to the seller or bidder) emails bidders in a currently open auction, offering a similar or identical item at a price below the current bid level. This siphons off potential sales away from the registered seller and makes an end-run around eBay’s fee system.
- Bid discovery, which happens when the bidder places a very high bid on the item (well over the current high bidder’s assumed maximum bid level) and then retracts the bid. This returns the high bid to the former high bidder, but at that bidder’s maximum bid levelwhich wasn’t previously public.
- Unwanted bidding, which happens when a buyer is warned away from an auction (because of poor feedback, past experience, or other reasons) yet persists on placing a bid. If the seller reports you to eBay for this offense, you can be indefinitely suspended from the service.
- Repeatedly backing out of transactions. Backing out of one or two transactions won’t win you any friends, it also won’t get you kicked off eBay. However, if you back out of a lot of transactionsas either a buyer or a sellereBay will toss you off. It’s chronic incomplete transactions that eBay notices.
- Auction interference, which happens when a bidder sends threatening emails to other bidders to warn them away from a seller or an item. You’re not allowed to interfere with in-process auctionsand you’re definitely not allowed to threaten other users! eBay will bump you if they find out.
- Transaction interception, which is out-and-out fraud. You represent yourself as another eBay seller, intercepting the ended auctions of that seller (generally with forged email messages) and convincing buyers to send you payment for the items. Getting caught at this one will cause you more trouble than just a simple eBay expulsion.
- Spamming, which occurs when you send bulk email (spam) to masses of other users. If eBay finds out, it’ll kick you off, simple as that.