What the hell is "Great Firewall"? (or officially known as "The Golden Shield Project")
Search for 六四事件 (Tiananmen Event) in Shanghai last month, you got a typical view of "Network Error" due to the Great Firewall. Click and click to zoom in.
Some contents in Wikipedia are also filtered by the Great Firewall. So if you study in China, you may not be able to dub "source" from wikipedia anymore.
Even some web sites we browse everyday are blocked, including xanga.com. Thats probably because reading your friends' dairy is "not an appropriate act for general citizens and may cause potential harzard to the national security".
HK is successful for being a free port. People enjoy a free market, freedom of speech and publish. Go onto street and protest if you dont like the government; buy a entertainment magazine/pornography if you want. Freedom is good for your health! Free-flowing information from mass media alert you to poisonous foods and fatal diseases.
If China was a more open-minded country, it could have run such a overwhelming Olympic n-year ago (where n is a positive integer).
Learn the issue in depth (it talks about HK too):
http://hk.youtube.com/watch?v=IWsXhNJFj78