Ning: A Framework for Building Social Software Apps
When I checked the site out, I was blown away.
Ning allows you to easily create social software applications that include tagging, commenting, favoriting, etc., in addition to providing hooks so that services like Google maps can be integrated easily into an application.
Building an application that lives on the Ning network will be a huge help in getting an audience for your application, which is key when building a good piece of social software (no users = antisocial software). Because it's supposedly easy to develop applications rapidly on Ning (which I can't yet vouch for--I'm still waiting on the developer account) and because Ning applications will have a built-in user base and be able to take advantage of network effects, Ning has the potential to dissuade some less-motivated people from starting new social software businesses.
On the other hand, a developer is limited by the Ning framework, and there don’t appear to be opportunities to make money from it, so a motivated team will likely still go out and build something themselves. This should spur a wave of innovation in niche verticals where the benefit of having a quick and dirty, somewhat inflexible application outweighs the downside of not having the application at all. This, when you think about it, is pretty awesome.