Picking up on the comments from Nigel and reply from Colin in Competition feedback.
I think we all agree that phones should be silenced during presentations. They can also be distracting even if silenced. If you are at the back of the room and they are being used in your eye line it's impossible to ignore even if they are being used for "legitimate reasons".
Also as a presenter seeing someone's face lit up by a screen can be disconcerting, is the person taking notes or doing something completely unconnected?
Perhaps it's a minor inconvenience we have to learn to tolerate!
Cheers
Bill Fleming