This is something I spotted a few months ago which I have reported to ebay.
I was selling an item and I noticed that a bidder who was the highest bidder placed 4 bids on the same item over two days; no other bidders had placed bidis. At first I thought the bidder was just desparate to win the item; he did actually win but only after several other bids were placed. When he collected the item I mentioned that I had seen he had put several bids one after another; he did not say anything but the look on his face confirmed that he was up to no good.
A few days later I noticed that the same occured on some of my other items for sale from other bidders; this happened more on very low value items. I then realised that the bidders were placing consecutive bids with very small increases in the maximum value of the bid. Other potential bidders would see this and like I thought at first; the current highest bidder is desparate to win the item; it is not worh bidding. I also noticed the same happening on other auctions; this can have an impact on the final value of the auction being lower than it should be.
I did report this to ebay and suggested that they implemented a system that if the current highest bidder placed another bid it just increased the maximum amount of their current bid and did not create additional bids; so far they have not changed the bidding system.
There is not much you can do in this situation; either cancel the auction and start again or cancel the bids form the bidder. I also block the bidder from bidding on my future auctions.

