Microsoft exec Jeff Dossett really joining Yahoo after allMountaineer, philanthropist, and longtime Microsoftie Jeff Dossett has a new claim to fame: He's brave enough to join Yahoo — but it took a while to convince him. Two months ago, Dossett, who joined Microsoft in 1991, went through a curious back-and-forth: BoomTown's Kara Swisher reported he was leaving Microsoft to join Yahoo. A Microsoft rep promptly denied the report, claiming Dossett was leaving a job at the software giant's MSN Web business, but looking at other opportunities within Microsoft. We could speculate about how Microsoft and Yahoo were bidding for Dossett's services, but the real lesson here is: Never, ever believe a Microsoft flack. Dossett replaces Scott Moore, who's leaving Yahoo as reported.