There you sit on a modern jetliner with a million things to do, your laptop, Kindle, smartphone and iPad at the ready, and in an act of massive hostility to the ethos of American productivity, the flight crew orders you to shut everything down for takeoff or landing.
Is this irritating inconvenience really necessary?
As far as obeying the instructions of your flight crew, the answer is YES.
As far as having any basis whatsoever in fact or science (that the electronic signals from all your equipment might interfere with anything on the aircraft's systems), the answer is a resounding NO.
Confused? So is the FAA, which has essentially refused to undertake the appropriate research on this issue since cell phones popped up in the mid-80's.
Back then, when handheld cell phones were as big as a brick and put out a whopping five watts of analog power, the FAA turned to the Federal Communications Commission and asked whether such devices were safe. "Does it look like we have wings?" was the unofficial response of one FCC staffer at the time -- an individual who helped draft the letter back to FAA pointing out none too delicately that things that flew were the FAA's responsibility, not the FCC's.
The FAA disagreed, of course, and after more than a quarter century, both federal agencies are still in a standoff with neither willing to put forth the funds and the time to determine once and for all whether passenger electronics have any scientifically-proven potential of disrupting an airliner's equipment to the degree of compromising safety.
Now, here's where it gets interesting. In the absence of the government answering the question -- and with personal electronics proliferating -- the airline industry threw up their collective hands in collective disgust and decided they were honor-bound to take the most conservative course of action: If personal electronics weren't certified safe, they wouldn't be allowed on during the most critical portions of flight, which are takeoff and landing (when accuracy of cockpit instruments is critical).
Meanwhile, the FAA -- still sidestepping the responsibility of doing the appropriate research -- recognized that the numbers and types of personal electronics were accelerating so significantly that if they undertook the task to individually certify each type, the agency would be doing little else. Worse, if they ever got it wrong and something bad happened, there would be hell to pay in public and Congressional criticism (federal agencies are, at heart, paranoically risk-averse).