My friends and I live near each other. It's a quick 10 min walk to their place and we have keys to each others' places. We've slowly lobbied more people to move nearer and life is getting better with each additional participant. I'm a firm believer in optimizing for our relationships. That said, we did that because it seemed to us to be the obvious right thing, and it seemed that our parents benefited from doing this…
When I was younger many of my friends and their friends all moved into my apt. complex. It was great.
Now that we're older, I'm in the process of fixing up a place abroad I hope that many of us can stay at once people start retiring and/or scaling back on work. My wife and I are going to move soon enough, but we've already let our friends know we have space for others. I don't mind building the beachhead :)