Check out this article at The Guardian on how you must do surveillance in order to implement censorship on the internet. In brief, the issue is that a network is an object that routes traffic, and it routes traffic without judgement or prejudice, so in respect to a network there is no good traffic or bad traffic. The result is that if you want to censor traffic to or from a particular address you need to interrogate all traffic and compare that traffic's origin and destination to a list of forbidden locations. Surveillance is the part where you interrogate all traffic. This is like listening to all the phone calls or opening all the packages. And that is the same as guilty until proven innocent.
But what really makes it silly is this: spoofing the origin or destination of internet traffic is only moderately hard, so people highly motivated to not get caught--criminals--will still not get caught. And for the rest of us, our every move online gets recorded in a big database.