I grew up playing Atari at a family friend's house, and saw my first real computer (a Mac Plus) around age 8 or 9 which I feel was maybe my first transcendental experience with technology (drawing with the mouse in MacPaint). I can't even imagine what effect a fully-connected smart tablet would have had on my intellectual and emotional development.
I'm just going to throw this out there, that we shouldn't be thinking of this as internet addiction, but more like, I dunno, asking a kid who grew up in space to live with gravity. Old folks like me (gen x) see kids on tablets and feel this understandable sense of concern, but forget that they are dabbling in their own little infinite universes just like we did. That doesn't release companies from their ethical responsibility of treating children with utmost concern though.