Known is targeted towards individual users - our aim is to get people posting to their own domains. But you can syndicate to sites like Twitter and Facebook, so you don't lose any audience or reach by doing so. It also runs on the Indie Box, and is designed to be installable on all kinds of services. It's open source, but there will also be support services & an easy hosted version if you prefer. And every page is an API endpoint, so there's massive potential for mobile apps etc.

More info: http://withknown.com