In a live context where people paid to see you perform?

Inexcusable.

On a TV show, it's a bit more understandable, but still not right.

and I'll take it even further: bands that use pre-recorded material in a live context suck. ELO got busted for their string sections playing "air-violins" in the late 70s when they had the big flying saucer-stage tour. Bogus.