It's interesting to think about what global public media might look like. Does Wikipedia offer a decent model?
The trick is balancing public-service operations with the ability to make quick decisions and maintain a user-centered design. Many open source projects go off the rails by adding too many layers of bureaucracy, and it's important that something like this is able to react quickly and compete with non-public versions. (How the BBC competes with ITV in the UK is analogous: the quality and finger on the cultural pulse is at least as good.)
I think the time is right for someone to try this. The question is, who, and where does the initial funding come from?
(Maybe it can come from Ev?)