Clearly a silly rule. It's designed for no other reason than to prevent us from being distracted during critical stages of the journey.

There must be several phones left on during take off and landing (I've seen one pilot on his phone during take off). I'm an avid viewer of "air crash investigation"; they must be saving the thousands of episodes filmed daily where lives are endangered due to a Kindle Reader.

As long as sound is off and headphones not in, there should be no problem. It's no more distracting than reading the safety card.