A few months ago, at Trans-Siberian Orchestra.
They spent about 60% of the time on a melodramatic, religious, badly written poem about an angel who comes down from heaven and cures some kid with a brain haemorrhage who sucks at baseball or whatever. When there was actually music, they weren't even playing their instruments. The singer was lip-synching, and the guitarists were both clearly playing power chords or resting while exuberant solos were coming out of the speakers. The drummer was the only one actually playing. I'm not just guessing either... I play all of these instruments, so I could easily tell, and even my musically incapable mother could figure out that they were faking.
I left halfway through. I couldn't sit through another hour and a half of that dreadful christmas poem.