Nothing. I don't think facebook membership counts are a good measurement.
Or possibly they are accurate measurements of the rates of Facebook use among these two groups. Maybe it's a good thing if people who are concerned about existential risk do serious things about it instead of participating in a Facebook group.
If it's worth saying, but not worth its own post, then it goes here.
Notes for future OT posters:
1. Please add the 'open_thread' tag.
2. Check if there is an active Open Thread before posting a new one. (Immediately before; refresh the list-of-threads page before posting.)
3. Open Threads should start on Monday, and end on Sunday.
4. Unflag the two options "Notify me of new top level comments on this article" and "