Don't make that kind of stupid mistake. Almost everyone has a list or 8 of proxies they use when they want to remain anonymous. This does not stop anything except prying eyes. Why? Logs... everything, including misconfigured WinGates, have logs. I have never seen a proxy w/o logs. If someone has the time and effort, they'll trace you through a proxy. But this does keep the anonymity much better than normal. This allows viewing of sites unavailable on one server for whatever reason, stops prying eyes, and, unfortunately, is used to disguise ones illegal activities. This is utterly stupid.. remember DOD? They had their own private network, they had their own proxies.. they were caught, anyone can be. People do it nontheless. If someone hosts a proxy... or even uses their own IP to cause abuse and that IP is dynamic, you just damaged your own cause. This could become huge within only a few days.. entire IP blocks from countries around the world banned from half of google...
I think the blocking of Asia is wrong and racist, but I see the meaning in it.. has anyone ever been to South Korea? In Seoul I saw people selling pirated software on the street. It was obvious enough what it was.. you don't find this anywhere else...
But the blocking of proxies? Impossible without tremendous damage.. and you won't prevent all abuse, but you will prevent legitimate visitors and a lot of them.