There was a recent news about China's prisons using prisoners to perform gold farming. http://www.guardian.co.uk/world/2011/may/25/china-prisoners-internet-gaming-scam

In many ways, the story that was picked, regardless of the extent of truth, retold imaginaries. I spoke to a Chinese friend about this story. He told me that it was probably true. However, it was also likely an isolated case. He was less convinced that this practice is widespread across China's prisons. The prisoners played online games by night, which suggested that the prison officials might have done this without the Chinese government knowledge.

Year 2004 was indeed when gold farming boomed in China. Chinese gamers paid high price for rare virtual items. Today, with many more Chinese companies engaging in gold farming, the practice is likely to be much less lucrative.