Kelly, I'm not a "vet" in terms of being a CH.com alumnus (I think my title says I'm a vet?), but I've got a thought about your question. I've been around and posting here since some time in 2006. I have learned SO MUCH from this site and gotten a lot of support for myself and for Gary (Thank you DJ and Steph!!!!!!!)
...But I've also gotten my share of shit - some of it I deserved. Some of it I still don't think I did - BECAUSE people don't know me or Gary, and I don't owe anyone any explanations. So I get stomped on, I take a break, I come back. I always come back because Gary has a problem and docs haven't been able to find him any relief. Yet. And they're still calling it CH.
Two-plus years later and I've connected with a few people, but CH.com isn't my "home." Maybe that's because I haven't actually met anyone in person and I'm "just" a supporter. Or perhaps it's because I only just recently started reading and posting in this, the general forum. But because I've started participating here, I've added quite a few people (and families) to my "prayer list," and I really care about what happens to them, even though I don't know much about them beyond the trouble they've posted here. But it's because I took the time to read, and my nature to care. However, in any site that's dedicated to a topic that's been around for some time and has a "general posts" kind of forum, people are going know each other, be friends, or become friends, and as a newbie you have to be willing to just "jump in." If it's too hot or too cold - either you adjust, you try again, or you get out.
For the people who come and go because it's hard to "break in" to that circle of friendship? As you point out, it's not a social networking site. It's here for people to learn and to share experiences. If we're shy, it's not the board's responsibility to help pull us out of our shells. If we're thin-skinned, it's our loss.
Friendships form - from people meeting each other, from the conventions, from people reaching out to each other, from people connecting because they're like-minded, because they can tell they like someone from they way they post and what they say....
You put yourself out there publicly, you subject yourself to public opinion - and either you have the personality to stand up to what comes or you don't. There's absolutely nothing to do about "cliques" in a place where they exist simply because the sites have been around for a long time and people have had the chance to meet each other. ...and I'm sure DJ and Steph do their absolute best to make sure that everyone gets treated fairly. Because there was a problem, they enlisted the eyes of others.
IMO there isn't anything to do about people leaving because it's tough to make connections. Maybe they should go to the O.U.C.H. convention! But as you so aptly point out, the site is still here for us to learn from, whether we chose to participate or not.

Laurie