Omfg
It was fun!
Well, there's a good number of people that got "run off" because they grew tired of the constant din of doubt on issues where they were subject matter experts, but they're still friends to me. BUT now the community loses the benefit of their perspective and I still have access to them and they're still friends.
As social media expanded, the dynamics shifted where "Hey, I did something good" and getting shouted down or literally, "When I was a flight test pilot and aeronautical engineer at Boeing" "You're mean because you contradicted when I read on the internet" — people just tire of that and leave one of the circles.
Honestly, there are things I've love to share but I think "Wow, I know exactly who will talk smack, I know exactly those that are going to call me a braggart and I know the other people that are going to think I'm an arrogant ass, let me just share that with a tight, curated group of people" because even I don't want to deal with it sometimes… and I built the site.
Hopefully my problematic Venn diagram will elucidate why certain people know certain things that other people tend to know, and also an instructional guide on how to get in and stay in that circle.
Every group of humans with common interests has this. Online or offline.