I found it interesting that as much as the author couched their arguments in "the causality isn't certain" etc they seemed very determined to blame smartphones for everything. And at least where decreased independence of "iGen" is concerned, I think they were wrong; I think helicopter parenting came first. And the worst part is, it wasn't just a couple of parents, it influenced culture and it influenced law enforcement. So even if you believe that your 9 year old is perfectly capable of going to the park, or your 4 year old can hang out in a locked car for 5-10 mins on a cool, cloudy day, neighbors, passers-by, and police may not share your confidence, and may cause you trouble (examples pulled from high-profile news stories). There's basically a widespread cultural idea that kids *should* be supervised at all times...and I do believe that hampers their independence and maturity in more than just those specific ways, because all of development is tied together. And when they find a place (albeit virtual) where they're allowed to have the socializing and privacy and independence they crave, of course they embrace it.
As a sidebar, I don't really understand hating social media for the content. The content is produced by the people you are supposedly friends with. If you don't care for them to share what's exciting in their lives--their trip, their new pet, their new baby, their new kitchen, their accomplishments at the gym, the new recipe they tried, ideas and causes they're excited about, etc--why are you friends? They seem to be adding nothing to your life! I also love to be proud of my friends accomplishments, and happy for them when they can meet up, or travel, or have a beautiful wedding, even if I wasn't invited or couldn't partake. Yes, I'm human so sometimes I'm in a mood and I do have those thoughts like "oh, why didn't they invite me?" or "I want to go to Europe" or whatever. And then I facepunch myself because I learned back when I was 12, 13, 15 that people *gasp* had relationships that didn't include me, same way that I had relationships that didn't include them; that jealousy was a stupid, useless emotion that only undermined relationships; and that if you're lonely *YOU* need to take the initiative and plan something, rather than waiting for someone else to invite you. (PS I've found FB to be pretty handy for organizing camping trips, potlucks, beach trips, and so forth...just sayin')
Back to the topic of teens/tweens...in spite of all the contraindications, I think it would be more harmful, individually, to ban a kid from the tech and the communities. You'd be setting them up to be ostracized and bullied if they're the only one (or one of a handful) that don't have access. But like any tool that cuts both ways, there does need to be a period of supervision, and teaching. My intuitive sense is that elementary school is too young for anything but using parents' phone to play an occasional game or video-call gram&gramps. High schoolers, especially older ones, I think ought to have learned proper behavior and earned some right to privacy at that point (perhaps not each one, but in general, or at least the "good ones")...it's just embarrassing to have your parents snoop your phone at 16 or 17. So I guess 12-14 makes sense, in my mind, for a kid to use a phone as a strictly regulated and supervised privilege, not a right.
Couple other thoughts that just didn't seem to fit anywhere... I remember not liking having my dad read/watch what I was doing online as a young teen...not because I was doing something wrong/forbidden! I was just embarrassed. As an adult now, I can see he just has a tendency to be casually dismissive and belittling, and I can see that as a flaw and I have learned not to take it personally. But as a kid, I didn't want to additionally expose myself to that by having him read what I was emailing my friend or whatever. Take your kids seriously, and reaffirm the little silliness as good fun so that they can come to you and will listen to you on the big things. Yes, it can be hard to tell...which is my second point. Teen girl drama is eternal. It's happened in person, it's happened over the phone, it's happened through email and blogs and on AIM/gChat/WhatsApp and on myspace and on facebook and now on instagram, snapchat and it will happen on whatever comes next. I think fighting it has more to do with building relationships and teaching kindness than anything technology-specific. Technology can make poison and vitriol easier, but it has to be there in the first place. Know your kid, their friends, the friends' parents, the teachers, the coaches, etc. Talk about what (social/verbal/cyber) bullying is and why it's not acceptable (the "toothpaste lesson" comes to mind:
http://meaningfulmama.com/day-62-kindness-with-toothpaste-week-9.html), and also how to fight it as a bystander. Help them build and maintain relationships with kids from other circles (outside of school)--maybe from sports, or camp. I think one thing that saved me in the middle school/early HS years was that I had a pretty close-knit group of family friends (families met/bonded through each other on a cultural and language basis), so even on the occasion there was a social falling out at school, I still had friends to confide in or proverbially cry on.