Most of the time, they will have a seperate account set up to do that for them. Generally with very low feedback numbers and generally bids only on the items of the same seller.
I've seen this happen a few times on auctions I'm interested in. It's such a shame, especially if it reaches a price that the item really isn't worth.
As others have said, the best you can do is spread awareness that the particular eBay user does it. It really sucks that eBay themselves don't find any issue with it.
I think the issue from an ebay point of view is that with shill bidding, unless it is so obvious its not funny, then its ok as it drives up the amount of money that they can claim back from a seller when the item sells.
On a side note, I am hoping this is a case of a different person, but it appears that a 0 feedback ebayer has purchased an item of mine on ebay through BIN. Now after 3 days there has been no payment made, nor any contact made from the buyer when an invoice as been sent. No I am hoping that the ebayer isn't an account from someone who uses it to shill bid just to teach me a lesson for speaking up against this. I may sound like a broken record, but I use my card sail to fund other purchases for my PC and tend not to put to much fat on the top of my sales in this regard. I am a little dirty that I got someone offer to buy then be uncontactable for 3 days since they purchased.
What's the bidder Id that purchased your item?
Had this sort of thing happen to me a few times, they keep creating accounts and bidding but never pay or no contact! P#*#es me off.
After no contact for 24 hours from a resent ebay invoice, and 4 days after the item was clicked as BIN, I have launched a non payer claim through ebay on this one.
Not even sure that the guy is legit. He is a WA registered ebay account.
Tell me - is a shiller just someone who bids on their own auctions ? Or also someone who has others bid on their auctions for them to raise the price ?
I have noted 3 days on my auctions for the pure reason that I believe if you bid on something or click Buy it Now, you should be having the funds right there and then.
I mean you don't walk into a card shop and say I'll have that card, walk out of the shop without paying and then don't speak to the shop ever again.
EDIT - I should point out though that after 4 days you are within your rights as a seller on ebay to launch a non buyer case. If this person came to me within the first 4 days and said "You know I am trying to put the cash together can you give me to XXX day, then sure I will wait. There are guys on here that I know have done that for me, and I am more than happy to pass on that courtesy. However with no contact, that is just poor form. A quick message and I am happy.