It's for yoo-hoo!

What do you do with mobile phone users once they enter the hallowed portals? I have noticed four general tactics when I have visited libraries:
1) the patented Dorothea stare - this usually works, but takes years of practice to hone. I can nail a mosquito at 30 yards.
2) uncomfortable shuffling and surreptious looks followed by member of staff sidling over and asking in an embarrassed sort of way if they would mind, you know, er, turning it off, it is, you know, a library, right?
3) the stroppiest member of staff being sent over to tell them in no uncertain terms to switch it off before it gets flushed down the toilet.
4) studiously ignoring them in the hope that they will see sense and retreat - this never works.

Or do you have a tolerance zone, a chill out area, where people can bleep and chirrup and tweet in freedom? I bet you can guess what Dorothea thinks of that.