One thing I find really annoying (especially when there's a problem with time running out) is extended frivolous dialogue used to set up a song however, I do appreciate some songs require pre-explaining. I was at the butt end of this type of selfish behaviour a few years ago. The chosen "penultimate" singer spent longer spouting out his preamble than he did singing his lengthy ballad that followed. So much so that, the session ran over time and ended the moment he finished.