I generally don't have issues with bad offers. Either the other guy comically overvalues his own players, or it's transparent that it's an initial low-ball offer, and if I'm interested in making something happen, I'm supposed to make a slightly more rational counteroffer.
Along with someone backing out of a deal, the other thing I hate: when you've had long, productive talks, and you're about to wrap it up, and the other guy says, "Oh, and add your 1st rounder or Player X (who's the best player in the deal). We're good?" Come on, man.