I’m in two groups.
I don’t have time for anything else. Too many other things to do.
I too am in a stupid number of groups… I see things that catch my eye and will join. I do need to go unjoin some that I’ve never really posted in. I will keep the local ones and I’m in a couple that I do post to. Like all of you, I like this site better than ravelry… 
Sort of the same here. I’m in a lot of them, read a few, post in less.
But all of them represent something I’m interested in, do regularly, or have.