This. I mean, I can understand obsessing about the teen / YA demographic if that's who you're selling to, but the idea that what they do represents some ground-shaking historical shift, and not just a (fairly well-understood) phase in normal human lives is just ridiculous.
For me, one of the most interesting things about this piece was the total bafflement with Twitter. Not that they didn't like it, they just didn't get it. At the same time, concerns about professional life were largely restricted to "Who will be the first to hire me and will my social life be used against me?"
In other words, the way that a lot of Twitter users treat the service as a huge and never-ending professional conference (with frequent flurries from actual conferences) is totally lost on people too young to have reached this stage in their working lives.
My takeaway from this is not "Kids don't use Twitter, Twitter must be doomed". It's that Twitter is for grownups (mostly), and that it's normal for people to age out of some networks and into others, just like they age into and out of music, cars, clothes, jobs, neighborhoods, and pretty much every other aspect of cultural life.