The talk of artists using their own SEs prompts me to put the other side. Early on as an SE a reasonably well known band provided their own SE and I let him take over. The guy knew nothing and the sound was a complete disaster! We spent half their set edging him off the desk and the other half getting everything back to where we started. Of ciourse they hadn't turned up for a sound check. This is not, in my experience, unusual in folk mucsic. Ever since then I have let the artists SE advise but not take control - at least not until I have confidence in them. After all it is my reputation that is a stake, not theirs. Bad sound is always the SEs fault ;-)

Its a careful balancing act.

Bob