What a great article! I am lucky to live on a cul-de-sac and we have 14 kids from toddler on up. There are usually at least 5 of them outside at any time during daylight, non-school times.
They are usually unsupervised but my dd knows that she has to stay with them and there needs to be at least one older kid present. It's great because they play all the traditional things like jump rope and kick ball and use sidewalk chalk. THey have bike/scooter/trike races, play hide and seek. I love it. I noticed that the family whose kids are not allowed to go outside unsupervised are not nearly as social when their mom agrees to let them outside while she's working in the yard or something. They are hardly around because when they out of school they are usually in some supervised class or activity.
When the little ones play outside, we always have at least one or two neighbors on lawn chairs chatting and keeping a loose eye on the kids. I remember the days when I could bike with my friends all over the neighborhood. When my dd is older I will let her do that with a group of friends, but not as freely as I did. I was allowed go to the local park and the KFC and even the mall!