True about the pissed up loud mouthed revellers, but don't forget that they're doing the same thing the guitarists are doing, i.e. cranking up their volume so as to be heard over everyone else. Amplification gives people permission to talk during the music, and loud amplification gives them permission to shout and jump around.

I host a concert series in a quiet room with no amps at all, and our audiences don't even breath heavily. It's instinctive. I've never asked them to be quiet; they just understand right away that if they make any noise they're going to spoil it for everyone. The only whip I have to crack is with the performers. Almost everyone wants to be the exception and bring just one tiny little amp. But they can't, and afterwards they're always glad they didn't.

That scenario wouldn't work in a pub or coffeehouse, where there'd be hissing espresso machines no matter what, but even there you've got to consider the competitive factor. You need someone with a sense of perspective controlling the amplifier volume.

I went to a coffeehouse a few months ago where people were jamming old-time music using acoustic instruments with pickups and microphones. It was an open jam, so everyone brought their own amp and set their own volume. The result was like a rock concert or a jet engine. There were no customers other than the musicians. It was painful to be in the room.