are you people serious? Why would you even bother watching a person play a single player game? especially if it bothers you that much. And does it occur to anyone that if the person is trying to socialize while playing a game they're probably not doing either very well?
A lot of the reason people seem to find it annoying is that the other player is "missing the obvious things" are these obvious after you have played the game three or four more times than the other person? Does it go away when the other person starts finding and doing things that never occurred to you?
It sounds like we've got more than one gaming-ego expressing itself on this thread, and I gotta say, as far as pet peeves go, this one is just nuts.