I have. Often it's me. This is usually when I'm acting though. There was one play I was in where I was acting alongside a fantastically talented lad who kept ad-libbing. I simply could not keep a straight face - but nor could the audience. I've seen professionals on stage trying not to giggle because the audience is laughing so much - I saw the League of Gentlemen live and one guy just could not get his lines out because the audience all knew what was coming and wouldn't stop laughing. I don't think there's anything wrong with trying not to giggle if it's the audience's reactions to your act that's making you laugh. It's a bit of interaction and shows you're acknowledging them and their opinions. There was no need for the article to mention it in a derogatory way, as if it makes people look unprofessional, as I don't think it does, personally - more that you're having a good time.

I've seen very few burlesquers lip-sync though. I have seen lip-sync used as a big part of drag queen acts, and I suppose there might be a bit of a crossover in terms of cabaret etc., but otherwise I can't see what they might be thinking of!

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