I am skeptical of the assertion that these teenagers have so little freedom. I'm waaaay out of touch with that age range, but from the little I've gotten to see, they do spend a lot of time on their phones, but they also do extracurriculars and drive places with their friends. I've seen kids skateboarding. I've seen them in loud groups at malls and bookstores. It doesn't look so different from my teenage years, except they have smartphones instead of IM, Starcraft, Xanga, and MySpace. Then again, this is just an anecdote vs. actual data.
I thought I was so cool pontificating on it when I was 15. Then I looked at it at some point in college... Dear God it was barely legible. I mean it was bad. More 2000-style internet abbreviations and text smileys than actual words. It was totally better than Facebook though, because you got to read what your friends were really thinking, and they read yours. Friends on Xanga were really your friends. Or your frenemies. Nowadays people aren't willing to read more than a sentence before they get distracted.