This has been something that's always made me wonder.
But I have a different take. For example on this forum (UBB) - I think I've been registered here for years, but seldom posted because:
1. I always felt stupid about asking help type questions - I always felt like I SHOULD know how to fix things. But I got over it.
2. It's a very male-dominated forum - so it's difficult to "break in" - but I've got over that too.
On my own forum, everyone knows everyone, and many people have been part of the forum for years. We also have an annual "get-together" somewhere in the U.S., so to new people it can look like we're very cliquey - although we're not. I've never been quite sure how to solve this problem.
