IMHO
We all know that cell phones have no effect on the on-board navigation system so what is the real reason for the airlines to ban them (and thank God they do)?
Frankly, I believe that to ban cell phones in flight is to lessen the possibility of air rage amongst those unfortunates crammed into their 17 x 32 inch boxes in the money earning section of the aircraft.
I regularly do 12 hour stages BKK to LHR and back again. If I had to suffer the sounds of various cretin's preferred ring tones and inane conversation then I might well become an air rage statistic myself.