as an engineer on the b777 and b744 for the world's fav. i can honestly say that just about everyone i know at the hangar during anything from a ramp check to a full d check uses their mobiles (secretly!) all over the aircraft, i know the thing isn't flying, but engines can be running and systems are simulated in air mode frequently and i've never seen any emi problems. not to say they don't happen, but just think more is made of this than is necessary. plenty of people leave their mobiles on silent during flights, enabling them to text & recieve calls quite discreetly - i accidentally left mine on on a longhaul flight and received text all the way.