From a Forbes Q&A with Beijing journalist and microblogger Zhao Jing, also known as Michael Anti:
Speed and access matter. In the traditional media era, censors could ban dissenting stories on a daily basis. In the blog era, along with other self-censorship methods within Web sites, the censors could handle the situation on a half-day basis. But in the Twitter era, things happen on a minute-by-minute basis. No effective institution could respond at this speed. Within minutes, bad news could spread around the world through re-tweeting. A quick protest could occur via Web 2.0 tools long before the government notices. Also, cellphones and the public platform of Twitter can make information leaks possible everywhere. Reporting is no longer the privileged right of media reporters. These are nightmares for an authoritarian system.
And, in the long run, the authoritarians cannot win.