I'm a little late on this one, but Sotheby's is suing a collector who consigned what was thought to be a Parmigianino to it in 2012. It sold for $842,500.
Tim Schneider connects the story to some other recent Sotheby's-related news: "The testing that pegged 'St. Jerome' as counterfeit was performed by Orion Analytical, the scientific-research firm that Tad Smith and company just acquired last month to help combat the industry's persistent forgery problem. While the house undoubtedly would have preferred to uncover the foul play pre-sale, the Parmigianino case doubles as a niche marketing opportunity. If you're a dealer or collector specializing in artwork of ANY past era, wouldn't you prefer to do business with Sotheby's––the auction house that can now definitively prove the legitimacy of the works it offers as a normal part of the consignment process––instead of Christie's, which has made no obvious effort to update its practices on this potentially costly front?"