The problem with free speech is the people listening
"In 1989, the [Chinese] government didn't know why Tiananmen happened. Now, by reading the Internet, they know what's going to happen. They know about movements in their infancy and they're able to kill them when they're still young"
...according to Chinese blogger Michael Anti. Ethan Zuckerman's summary of a Berkman talk he gave has lots of other fascinating comments.