Each new group of kids come of age wanting a space they can discover together and call their own. This is DNA, not computer science. It's not about tech changing (oh, this is Facebook if it was build only for tablets) - it's about getting to a dry piece of land when you're 13 years old and being able to plant your own flag. I don't see how you get beyond the anthropology of this.
If the sustainability of everything relies on 13-year-old kids then we're kind of all screwed. But that's not the point Walk is making and I do agree with him. The kids are evolving and will most likely reject a platform that their older sibling, or heaven forbid, parent, covets. It's a little bit like The Observer piece on ecstasy returning to the clubs: they found the newer generation of drug taker to be creating their own rituals in order to own it. It's all about buy in.