The people in my neighborhood with kids know each other
The people who walk their dogs know each other
The people who take care of a flower garden in their front yards know each other

I have kids, so I am part of group #1. I can probably name all the inhabitants in 10 different homes on my street... but then we seem to live in some sort of time warp. When the kids get home from school, they go play on the street. When they were younger, at least one parent was out and would keep an eye on all the kids from the block (while the other parents were busy doing chores or making dinner etc.) Now the kids are older and they just ride their bikes around the neighborhood or build crazy forts in the woods at the end of the street.

There has been more than one occasion when an emergency came up (e.g. kid got hurt and had to go to ER), and the parent says "hey, can someone take care of my other child while I run to the hospital?", and more than one hand goes up. They take care of the kid, feed him dinner, etc. until the parents come home.