To be fair, I never really liked Ning. When you go to a *.ning.com domain to check out a community, the front page is always this huge ancient 2003-web-style clusterfuck of boxes that just doesn't communicate anything to a newcomer. Can't speak for a regular, cause I never became one.
Now facebook groups are a somewhat similar clusterfuck, but the difference is that you're already on Facebook, so you already got a membership and don't need a spiffy 3-paragraph web2.0 marketing introduction friendly GET STARTED link.
Ning tries to be all these somewhat separate communities, plus they're not as big as Facebook, so whenever someone might want to join such a place, they are new, and are going to need to be taken by the hand.
This is somewhat similar to the Elevator Pitch thing I told you Cram, but the reality is that also Ning isn't very helpful in guiding you that way, at least, most of the other communities there also never seemed really "open" for outsiders, easy to immediately grasp the sense of "what can I do here?".
BTW, seriously, if I want to get started with the Dreaming. What do I have to do? How do I get started? What is the minimum stuff I got to read?