I hate Chekovs Guns that get forgotten about halfway through the story.
I read an Aliens novel last year that had something like that... the first chapter elaborately setup the fact that the main character had the ability to basically federalize this civilian outpost that he was going to investigate. He gets there, crap starts hitting the fan, and.........the author just sort of forgot the authority he'd vested in the character in the first chapter because it would be a better story if the guy were alone and helpless.
A good editor really should have caught inconsistencies like that, but I don't think books are really edited for content anymore.