My neighborhood has a lot of kids, but is pretty quiet. In fact, I only know of one house on my street where the kids are regularly playing outside (front yard, usually with someone watching from the porch). There's a school with a playground and a field next to me as well, and it's usually empty. We also have a large wooded/swamp, never see kids playing back there.
And I live in a clean, quiet, "safe" suburb. Way before this story came out, I used to wonder (especially on snow days, or really nice summer days) where all the kids were. Again, mine are still very young (3yrs and 8mos) to be alone, period. But it was disconcerting to see that we live in an area where kids should be outside, but they aren't. Pretty sad that this generation with all its technology and all things that are supposed to bring us together, actually isolate us more.
I honestly think this is a huge factor. It's easier to play on your phone or Xbox than it is to go outside, where it might be hot or cold. But that brings me to my next point. One advantage with all this technology is that you can track your kids. I saw this little 2 inch square GPS tracker for kids and think it's brilliant. If people are so worried about their kids running around, why not track them? I'm sure there's things that can and could go wrong with this, but it's something worth looking into. Same goes for home monitoring cameras for latch-key kids.