This made sense until I got to the part that said it was forbidden to communicate with others according to the rules of the experiment. This, to me, makes the experiment less convincing and the outcome less of a surprise.

A lot of online activities, no matter how brainless, are social. It doesn't seem fair to say "kids can't live without their mobile phones" when it's really about them not being able to communicate. I'm pretty certain the results would be less drastic if they could have just hung out and played boardgames.