And, at least two years ago, could be trivially worked around if you bought appropriate SIM cards in Hong Kong, which - apparently completely legally, and with cooperation of one of China's telcos - gave you completely unfiltered access in the Shenzhen area.
Sadly, I learned about this only a month into my stay in Shenzhen; before, I was playing the BPN cat&mouse game.
China seems to have a weird dual stance about GFW. I even heard rumors that companies could pay someone to get a legal, unfiltered link.