Do you trust auctioneers and their software enough to automatically outbid the competition up to a limit? I cannot bring myself to leave a secret maximum on their websites, suspicious of any auction staff who might have access to it and pose as a counterbidder. Would love to read your opinion on that.
I know of a court case dealing with precisely that. But that was before specialized software companies and portals started taking over the bidding part from most auction houses. It remains a matter of confidence. You don’t know whom you are entrusting with your final bid. And one thing’s for sure: computers are not discrete; it all depends on the conscience of the guy behind their monitor.
I've done it before in the past and won one time with the maximum I left and another time a bit below it. I won't do it now. I don't trust auctions at all.