Hi Pete,
A couple of years ago I was having some of my auctions sabotaged by a bidder in Italy. I was selling antique photo equipment at that time with reserves.
He would bid up the item to find out what the reserve was, if he did not like the price, he would proceed to cancel his bid during the final hours of the auction. Not only did his high bids keep other from bidding, his withdrawal would destroy the entire sale.
After experiencing this a couple of times, I began to make a disclaimer on my auctions that I would not sell to him. This along with complaints to eBay finally got him removed.
It took an extreme case like this for me to go so far as to list his name on the public forum, but he pushed to far and I felt that it was justified. I believe that under certain circumstances the seller should have the right to protect himself and other serious buyers in whatever manner he feels necessary.

Take care,
Ron