I run a few google groups, and I have them set for invitation only, and not advertised on google itself. Means more work for me, but if someone wants to join, I ask a few questions about them, and find out what I can, before approving them. I've only rejected a few people, mostly who refused to respond with other than invective.
We could still "advertise" the list if you wanted, thru places like A2central.com, Juiced.GS, the usenet groups.
Howard