I can see the point you're making Kurt. But at the same time, I'm believing that the power of Ning is in offering the network capacities to anyone who wants to begin a network on a subject she/he likes and can't find any to its liking on that subject.

A worldwide network on about any subject imaginable is now possible, created out of nothing in almost no time.

Let these networks the possiblity of organic growth. The growth ratio of the networks might even be a better indication than the numbers you're asking for.

It's perfectly possible to kill of one of your networks at ning if you see it doesn't work at all and you don't find the time for it after all. It even gives you the possibility to start a new network (normal maximum quotum of networks for one person to start being ten).

http://webosophy.ning.com