They do so at their own peril. Peril, in this case, consists of pinching and scratching, but still. I guess standing around talking to friends is more important to some people than taking notice of strangers with striking good looks and brimming over with talent. That last statement is meant to be sarcastic, by the way. I certainly wouldn't stand around talking to friends if there was the chance of spotting a famous artist in our midst.* I mean, this is an arts festival, right?
*Note to self: get some friends, if only to support my thesis.