Here's an interesting news story called "The Internet in pieces" by Misha Glenny writing for the Guardian. The story tells how Iran has decided to block all access to the global Internet from within Iran and create a giant Iranian intranet. Ostensibly the reason is to protect Iran from cyber attacks like the recent Stuxnet worm. Of course a side effect will be to deny Iranian counter-revolutionaries access to Twitter, Facebook and all forms of external information. Whilst I can't see this being anything other than harmful to Iranians in the short term the potential for much larger countries, like China, to create their own web that has all the content and services that the vast majority of their population needs is clearly a possibility.
Chapter 12, Digital Underworld of The Universal Machine has more about Stuxnet and cyberwar.