I got that. I'm not willing to do that, so I didn't join the group. No hard feelings...
However, I do monitor this - If the Boost group is hitting a project that's on my list of goals, I'll join. I brought up ABC because I happen to be crunching it, and noticed other teams more than doubling our production.
Again with the "members only" forum. I still don't like the idea. As a potential compromise (if possible), perhaps we can have our Admins create a new Groups permission level where you can't see posting within the group unless you are a member of the group?