Well, this brings up another issue -- and maybe it should be a new thread -- about learning by watching what others are doing. In a thread sometime ago, one of the posters said something about a "fret hawk" at a jam, and the way he said it was really derogatory. He was referring, I think, to people (like, say, ME) who watch a player to see what fingering s/he is using. I do this because I'm very, very much in the learning mode and watching what others do is part of how I'm teaching myself.
But is it considered impolite to watch other players fingering? I mean, if watching our OWN fingers can break our concentration to such a degree, does having someone ELSE watch your fingering throw you off track?