It depends on the event. If it's a lighthearted event is meant to have some humor then it's fine, but at a heavy roleplaying/plot event I'd like it as serious as possible.
Aris' answer expresses how I feel too.
I think they have their place in all quests. Sometimes you just come upon someone who is a little silly during a serious moment. It's a good reminder that this is only a sill game we play.