I loved though in The Boy From Oz when everyone clapped along to Quiet Please There's a Lady On Stage.. cause well, you can tell everyone was really feeling it if you know what I mean!
I think the only time it gets to me is in Wicked, during the Regime Change scene. When after Glinda slaps Elphaba or Elphaba slaps Glinda, the audience goes like, "ooooooh." like the kind of in-your-face-ewwwwwww. I've seen Wicked 8 times now, and it happens everytime and it drives me crazy!!