Here's my take on Portable Electronic Devices:

Will the plane go down if you leave your fancy glass-fronted cellphone in "Airplane Mode" or, worse, leave it on in the overhead compartment where it will increase it's radio signal and try to scream home to mama until the battery dies? No. Not at all. Otherwise thousands of planes would have gone down and the flight attendants would have to wand the entire plane before takeoff.

Can your fancy glass-fronted cellphone turn into a projectile that can take someone's ear off if the pilot has to floor on the brakes to abort take off (200 - 0 in about ~8 seconds)? Absolutely. The _ceramic_ brakes on planes _Catch Fire_ when they have to stop like that. That is the level of kinetic energy you are dealing with in emergency situations. This is also why the laptop has to be on the floor or locked in a bin and can no longer live in the seat back.

So, if you put your cellphone in airplane mode and slip it into your front pocket, the flight attendant will not notice or care because you're not ignoring him or her and diddling the silly thing all through the safety breifing. If you have it out dinking around with it while the plane is taxiing about, it's something that becomes a pain-inducing projectile during hazards that passengers _can_ _not_ _see_ _coming_.

So don't get peeved if they come around telling you to shut it off and put it away. Had you been paying attention, you would have easily stayed off their radar.

Also, paying attention to the people responsible for your safety (The Main Reason for flight attendants being on a plane, getting you stuff is just a bonus) is just the courteous thing to do.