I knew a guy who mumbled so much you could never understand him. It was really irritating, but also the secret of his success. His job was to liaison with a number of governmental/bureaucratic organisations - involving customs clearance and things like that - and he was incredibly successful. No one knows for sure how exactly he managed it, but a leading school of thought was convinced that it was his mumbling. The bureaucrats just gave him whatever the hell he wanted as quickly as possible so that they could get him out of their offices asap.