Good question Jim, but let me turn it round.

I will clap and feel empathy with a mate in a pub who hit a few bum notes, forgot his words or tried to over complicate with less than flattering results, but would complain like hell if I had paid £25 to watch Martin Carthy or Martin Simpson and they played similar.

On a much lower level, i.e. me, I will hear something at a singaround and say "You know, that song is similar in storyline and certain phrases to one from the other end of the country. Let's see if I remember it." Whereas if I am at a concert doing my set, I have practiced over the years, got the songs just where I want them and the "spontaneous chat" between songs is sometimes word perfect to twenty years ago.

Like I said, group sharing of songs versus entertaining. The main thing they have in common is, to be fair to your view, that even in group thera.. er singing, the rest of us should expect you have either practiced it so playing at your level or are at a level you can pull it off and not waste three minutes of the lives of others.