Yep, I grew up hanging with the neighbors too. The older folks were like extra grandparents, the younger folks babysat us and then we grew into teens who babysat their kids, the men all helped each other out with chainsawing fallen trees or putting together the new grill, etc.
However, when I was growing up, most of the mothers were stay at home moms. They had more time to chat and form friendships that then carried over to the dads and kids. With most families having two parents working outside the home, the evenings and weekends are more time-crunched now.
I think of Saturday as the day to catch up on all the errands and housework and lawn work I can’t get to during the week, what with work and commutes and cooking dinner and getting the kids homework checked, etc. If that leaves Sunday as the only quality family time, and for many they spend half the day in church, when do I have time to casually get to know my neighbors?
The internet and cell phones allow me to maintain friendships that sheer geography would have made not so viable in my parent’s day. That college friend that lived 4 hours away would have been an exchange of holiday cards for my mom, whereas I can blog/IM/chat/email them daily and spend time getting together every few weeks. Why make new friendships with the neighbors when I don’t have the time to maintain them?