A new exhaustive study called "Access Denied" tells the whole story of Internet censorship around the world:
Many countries around the world block or filter Internet content, denying access to information–often about politics, but also relating to sexuality, culture, or religion–that they deem too sensitive for ordinary citizens. Access Denied documents and analyzes Internet filtering practices in over three dozen countries, offering the first rigorously conducted study of this accelerating trend.
(Thanks, Seth!)