I have to assume that anything I do on Facebook is going to be shown to everyone I am "friends" with on Facebook. Again, it's not going to be news to any of them that I talk about things with rationalists, but again I have no particular wish to advertise everything I do to everyone I know.

I think there real value in having discussion about rationality in a way where friends who aren't rationalists come to see them. It does limit the amount of jargon that you can use, but it has real benefits.