I have some sites that I want to be accessible in Shenzhen. They include being able to post content to my sites. Unfortunately many Google services are blocked in China. One such service is the recaptcha service for spam protection. Fortunately in the Google recaptcha FAQ, they provide a solution. It does not specifically mention China however when implementing this it worked.
The gist of the solution is that you need to replace references to “www.google.com” with “www.recaptcha.net”.