I joined and poked around a bit. No offense, but I wouldn't call that a group of startup founders. It's a group of people who want to be startup founders. That's the problem I've seen with these groups.
I don't know how much effect it has on the quality of the community, but I think it would be wrong(and could even be administratively overwhelming to manage that unless it is a paid forum) to exclude people who are new to the startup world.