Just after Sept 11 when all airports went completely mad about security. Women passengers weren't even allowed to take their handbags onboard. All cameras, cd players, walkmans and phones were conficated at the gate and checked into the hold. (This was at LGW).
When I asked a senior security person why all personal electronics were being considered as suspicious, he told me about something that had happened in Israel a few years ago:
A hitman had managed to secrete a tiny amount of semtex into his targets' mobile phone. The low energy microwave radiation emitted during the call would be enough to fire the detonator....then..Boom!
You can now take your phone with you on the aircraft, they just ask you to switch it off!