Down her, until now it's been illegal to block mobile phone calls (on the ground), but the law has just been changed to allow a trial of blocking in prisons. This led to a discussion on radio of mobile phones in aircraft. Most people were happy with the ban and would like to see it enforced, but a couple of pilots rang in admitting that they always left theirs on.
I can see it's important for pax to be attentive during the demo, but I'd like to think that the crew is as well.