Betting against the rich isn't easy.

Just ask short seller Jim Chanos, who for months has touted a bet against shares of Sotheby's on the grounds that the art market is in a bubble. That trade hasn't exactly panned out: Recent art sales such as the collection of legendary collector Bunny Mellon blew away estimates and Chanos took another hit Friday after Sotheby's said its controversial CEO was stepping down. The stock is roughly flat since Chanos pitched the short on CNBC in early April. It's unclear if or when Chanos took a short position and he didn't respond to a request for comment Friday.