We hear many stories recently about Twitter used by people in Iran and China to report about issues which the government doesn't want its subjects and the world to know about. Twitter is used very successfully in this fight, but the main problem is the service is centralized, so the government can shut it down and that's it for tweeting.
Google Wave will be released this year and I expect it will replace Twitter for such uses. Why? Because people can run their own Wave servers and those servers can communicate with each other, so there is no central point of vulnerability.
So people run their own servers and they use it for normal communication, but if there is an important event they can use the mesh of Wave servers to distribute information about the event. The government has no central server to shut down, they have to go after each individual Wave server which is much more laborious.
Therefore the future of citizen media is Google Wave, not Twitter. We only use Twitter temporarily until the real thing comes out. Work faster, Google! :)