I may not be correct about this, but here's the parallel that was running through my mind as I read this:

Ning is to social networks now as Movable Type was to blogs in, oh, say 2003. It's a private company that has found a way to make it dead simple for anyone to come along and make a social network of their own, what Movable Type did for blogging.

The article paints Ning as unstoppable, but if the parallel holds then the end I would foresee is the eventual arrival of an open source rival, a la what Wordpress brought to the blogging scene. (Whether that ends up being Buddypress or some other alternative I couldn't say.)

Thoughts?

The article spends more time extolling the virtues of virality than actually speaking to what Ning does.

I read page 1 and jumped to page 5 without reading 2-4 without a loss of continuity. Guess I saved myself some time.