Youtube appears to blocked in Mainland China by the evil Net Nanny.
Is it because of the 17th Communist Party Congress currently going on in Beijing?
The 17th Communist Party Congress is abbreviated to 十七大 (shiqi da) or ‘17 big’ in Chinese. Mainland Chinese soft porn website 17da.com and overseas-hosted hard porn link site 17big.com seem to be open for business.
Update: Marc van der Chijs points out the most likely explanation: Youtube just launched Chinese language versions of the website for Hong Kong and Taiwan.