In the following Video Andreas Bogk and Ralf Bendrath talk about the technical and political aspect of deep packet inspection. DPI is a technique to analyze Internet traffic, either to speed-up/slow-down certain protocols and programs or to alter/delete web content. This method is used by Chinese government and ISPs all over the world.
also check out my post from April 21st, where I explained the different blocking mechanisms. The post also has an interview with Andreas Bogk included.