What most people don't realize is that the usage ban on electronics is NOT based on signals interference. Regulators don't want you using devices because take-off and landing is the most dangerous time of the flight – highest risk of crashing or massive turbulence.
If you're paying attention to some device, and the flight has a huge dip from turbulence, *you need your wits about you* to react in the best interest of your safety (and possibly the safety of your children).
Historically, this kind of info was deemed to be (itself) a danger to the safety of the flight cabin – since if people knew these were the high-risk times, then a) any small danger could mentally be inflated and someone could throw a riot (hysteria), or b) someone looking to cause a problem would realize that this is the best time to make danger.
. :( deal_with_it.gif