Earlier this year, MSN exec Jeff Dossett climbed to the summit of Mount Everest in order to bring attention to the problem of AIDS and HIV in Africa. But now he's doing something really crazy. Dossett quit Microsoft last week and likely plans to join Yahoo, BoomTown reports. BoomTown's Kara Swisher notes that Dossett might be going because he's an old friend of fellow ex-Microsoft exec and new Yahoo exec Joanne Bradford. It's unclear what Dossett will do at Yahoo. At MSN, Dossett's job description labeled him as "the lead for audience, content and programming strategy and execution in the U.S," but apparently that was just his latest gig in a long line of online sales and strategy positions.Update: Dossett is not actually leaving Microsoft at all, Valleywag has now learned. That'd be crazy.