An excellent question at Forbes magazine:
All of which begs the question: if electronic devices are OK now, why have we been getting yelled at to turn them off for so long?
The answer is that we've been governed by regulations written back in 1976, when the dangers were more real:
Today’s announcement can be credited to an evolution in technology, says Thomas K. Eismin, Professor of Aviation Technology at Purdue University and author of two textbooks on aircraft electrical and electronic systems. “Early PEDs used more energy and emitted more electromagnetic energy. Remember how big the battery was in your first laptop?” He also notes that “older aircraft were more susceptible to potential failures.”
Now, he says, “Since all US carriers have retired their old gas guzzling aircraft and today no one uses a Commodore 64, the flying public should have no fear. Rugged design of aircraft electronics and duplication of systems” make the danger “virtually zero.”
I confess I've never been able to work up much of a mad over this. People can't stay off their phones and electronic toys for the realtively short periods of landing and takeoff without feeling that a hardship is being imposed on them?
I usually read on flights, but only once we're safetly in the air and before beginning the landing. When it's a real paper book instead of my Kindle, I could read on takeoff and landing, but I've never been inclined to. Ever since I read than most crashes happen during takeoff and landing, I've tended to be almost paralyzingly afraid during those events. I don't want to read or do anything else that would distract me from my abject terror.
I know what happens next. That guy who's on his cell all the time and just won't shut up will be seated next to me on every flight. Come to think of it, even abject terror would be better than that.
