New York Times:

BEIJING — While China’s censorship policies are prompting Google to consider quitting its operations in the country, some technology companies see the restrictions as a golden business opportunity.
More than a million people in China, including human rights activists and expatriates, are using special software to circumvent the nation’s complex online censorship system, known as the “Great Firewall.” This has created a booming market for software companies, which are capitalizing on the growing desire of China’s Internet users to fanqiang, or scale the wall, to visit Web sites like Facebook, YouTube and Twitter.
“More and more Chinese people know how to use this software now,” said Teng Biao, a lecturer on law at the University of Politics and Law in Beijing, who recently discovered that his Gmail account had been hacked, apparently by someone interested in his involvement in human rights issues. “It’s very convenient and easy to use. The government can’t fully control people browsing the Web.”
Although the technology is not banned outright in China, it is often the focus of censors, who aim to shut down sites that give users access to the software.
The number of people using proxy servers, virtual private networks and other computer tools to skirt barriers to banned information online is not growing just in China. The United Arab Emirates, Iran and even Australia are seeing a surge in customers willing to pay for the freedom they offer.