For many people the internet is an essential link to the outside world. For example in Iran, the opposition have little voice in every day media, but crucially they can speak their true thoughts online. Which is why the regimes like the Iranian government so heavily censor what websites can be accessed. Fortunately very few countries have mastered the ability to completely control access to the internet, the Chinese have perhaps come closest by pouring almost unlimited resources into the infamous Great Firewall of China and sponsoring rival social networking sites (controlled by the Government of course).
The technology is difficult though and trying to restrict access to random TOR exit nodes is a mammoth task. Even using simple proxies and VPN servers will allow you to bypass most restrictions. There are also some very sophisticated security software that provides many firewall/hopping, proxy switching features available commercially too.
The technology war will go on, with the Western democracies largely leaving the web unfiltered, instead concentrating on surveillance and data analyis – like the MI5 and projects like PRISM. Whilst the countries like China, Iran and Thailand slowly block access to more and more sites considered unsuitable for it’s citizens. This road however will probably lead to the scenario in North Korea, where in fact all external websites are blocked by default – a kind of Korean intranet. Thus the ruling parties will then decide – ‘not what to block’ but instead what you can specifically see – a whitelist of approved websites.
This is probably the only way a nation can completely control access to the internet completely. It’s likely to happen sometime in Iran if the current regimes maintain power – there are already Iranian alternatives to social networking sites like Facebook and Twitter all controlled and regulated by the authorities of course. Whether this happens in China is less certain, economic measures and reliance on free trade to maintain growth would be extremely difficult to maintain under this sort of draconian policy.