they ask you to turn them off because the landing and the takeoff are the most critical parts of the flight. they do it for safety reasons so that everyone is attentive in case something happens. that's not to say that some devices might not cause interference with the airplanes instruments (like cell phones), but no one really knows for sure it they cause any considerable amount of interference. some other flights around the world let you use your phone, but here FAA regulations require you to turn them off.
best thing to do is to listen to what those motherfukkers are telling you to do and not be on some ignorant shyt as if you know how an airplane works...
edit: oh, and on a sidenote, they might have someway of monitoring the interference. on a flight i took about two weeks ago, before we taxied to the runway the pilots said something about everyone not having their electronic devices off. i mean, maybe the flight attendant told them to say that because she spotted someone but i don't recall her going to the pilot's cabin. he just said something about it out of the blue...
ignorant arse...
@ Kanye I wonder what dude is listening to.
