One thing I'd add to my remarks on France 24's The World this Week regarding social media as tools for political protest. As I said on Friday, I'm an agnostic with regard to how decisive these emerging communication technologies are when it comes to defying authoritarian power. Certainly they facilitate information-sharing, which is one component of effective resistance. But it's not the only component, and it's far from the decisive one. Organizational networks, physical acts of contestation and/or the cooptation of existing centers of power -- whether the police, the military or some other determinant of social order -- remain essential to any effective challenge to authoritarian regimes.
Transparency helps drive public opinion, but public opinion also has a way of rubber-necking and then moving on. That's why Wikileaks makes for sensational headlines more than for actual systemic change. For now, the historical record seems to indicate that the same holds true for Twitter, in the absence of those other components.
On the other hand, I'm also agnostic when it comes to how effectively states can shut digital media down. States will manage to erect barriers to slow down and complicate the otherwise free and instantaneous transfer of information that social media offers. But they will never be able to totally block it. That was true in the age of the printing press, as the many historical records that still exist of banned and censored works attest, and it's even more true today.