According the to a New York Times article, Ning will no longer support communities as of next year. I'm sure this will help make the case for many of you.
From my perspective--promoting Ning for education--I think it's very good. It will likely mean that Ning won't have to be on a lot of *content*-filter lists. But I would guess it will still be on some because of the general user-generated content category Ning still falls into.