I've never had many friends, and definitely not really close friends, but that's fine with me as I'm a private person and don't really like to share too much. It doesn't worry me as I've always been happy on my own. I'm also wary because I've seen people get really close, maybe too close, then have a massive falling out and it just seems like too much drama.
We always used to make an effort to get to know our neighbours so we could say hello, pass the time, etc. but in the last 10 years we've only had nasty neighbours so I go out of my way to avoid them. If I was ever lucky enough to move I would like to think we have people around that I want to know.
Interesting what you say about penpals CLKD as I had an email friend for around 9 months and we got on great, then we met up and we just didn't get on, and never communicated again.