It seems like many of the topics covered donlt have room to expand. For instance: ice chewing. I chew ice, I realize that it's not normal, but I don't go on an ice chewing forum. That's like all there is to say about it unless you can find some kind of ice connaisseur.
Now that said, negative topics could work. You could find some ex-Childfree folks and ask them about what drew them to the community, what it was like, and why they decided to leave. Now it would be a one-sided discussion as these people would have reasons for leaving the community, but I'd definitely like to learn more about some of these communities.