Not sure if this is totally applicable to the thread, but one of my HUGE pet peeeeves is when a solid to incredible veteran act has to "open" for a new kid on the block with a hot single, ie.
Ash opening for The Bravery (when it was an ASH show no less), Sonic Youth opening/co-headlining for/with Yeah Yeah Yeahs, Pretty Girls Make Graves opening for She Wants Revenge, Muse opening for whoever the fuck it was they opened for a few months ago, Placebo NOT headlining whatever the phuck Linkin Park's tour is called AND co-headlining with She Wants Revenge, Dresden Dolls on that silly emo/boy band tour last year, Stereophonics opening for some douchebags I can't remember, ANYONE opening for the Killers, etc....