not quite, Ellery...
you can shoot an email over to the potential buyer to warn him. I was warned two years ago when I was a noob, and I took advantage of that feature twice to alert somebody else.
However, nowadays I see more and more eBay auctions with anonymous bidding history such as high bidder bidder7, second high bidder bidder2... I guess eBay does this to protect second high bidders from receiving fake second chance offers, but the downside is you can't warn the high bidder in those auctions anymore... oh, well.
Christian