I have not had much experience in this but I can only remember upsetting a professional band once. This was during a local festival and due to an error in booking, a few of us who were admittedly being paid beer money, ended up in the same venue as the other band and we agreed to do 2 3/4 hr sets each. They were happy at first but the trouble was that on the night, our little line up of fiddle, banjo, guitar and possibly bodhran (can't remember exactly - tend to peice a band together depending on who is available) went down far better than the paid band and you could see them getting more and more annoyed. The worst part was they were down for the finishing off set and after the finished, there were demands for more - more of us!!!

I don't know why it should have worked out that way and we are not that good (or we would be proffessional - at least I would go that way if good enough)but that was the way that night went and I doubt that band would ever welcome an amature folk band again.

Jon