Blue chin syndrome

Thinking further about this need to earn an audience's attention reminded of a phenomenon that Grainne Maguire, a stand-up comedian friend of mine, calls 'blue chin syndrome': -

The gig isn't going well when out in the darkness you see all these blue chins; audience member's faces uplit by their mobile phones as they text their friends

This is bad enough when the device in question is a Nokia.  If they bring out the iPads it's probably time to vacate the stage.