I don't think that the reason. The acoustic worked just fine at the 2 acoustic/electric shows I attended....and there were over 30,000 at each one. What I think is that Jon was having trouble last night and there have been equipment problems at the last few shows, not just last night. But being the perfectionist we all know him to be, he probably doesn't want a repeat of last night and decided to stick to the electric sets. He was mad about something...it was very obvious he was pissed off.