I dunno, Molly, I saw the Battlefield Band last February over in Forest Grove...Alan Reid said that if anyone gets the urge to get up and dance go ahead and do it, we could always do with a good laugh...
My feeling is that if people want to dance, since it is showing an enjoyment of the music, then great....I don't feel it detracts, but enhances the artist's performance....for example I have seen people up by the stage signing the artist's words, and they are literally dancing while they do it...I think it is awesome...
however if some one is singing along to the words...and loudly, and annoyingly...you should have the right to tell them to shut it.