The blogosphere has gone bananas over the Ning playground. From my quick scan of the developer docs and FAQS, we're talking about a hosted PHP app service, with some extra support for the fancy widgets of the day (tagclouds), webfeeds as sources and sinks, user/group management, and the ability to "clone" applications. There's no inherent support, that I can tell, for social applications, other than connections to many other Web apps which folks throw in the social bin.
Here's a challenge for someone who wants to build a social application platform. Come up with a calculus of social roles and boundaries. Design and implement a developer's toolkit that makes it easy for application writers to build social environments along a spectrum of concerns and expose social controls to their end users.
I'm surprised at how many folks have fallen for the buzzword compliance. Then again I have been known to be wrong.