One small piece of anecdata which kind of supports the theme of cohesiveness being important. I've been a part of a relatively small Stackexchange site (securi

One small piece of anecdata which kind of supports the theme of cohesiveness being important. I've been a part of a relatively small Stackexchange site (security.stackexchange.com) for 11.5 years and over that time I've made friends with other Sec.SE participants which have lasted to this day. Most of the early core users aren't that active on the site any more, but quite a few of us still hang out on-line and meet up when the opportunity presents.