The Yellow Turban Rebellion of 184-205 AD was sparked by "an agrarian crisis, in which famine forced many farmers and former military settlers in the north to seek employment in the south, where large landowners exploited the labor surplus to amass large fortunes." According to Wikipedia "The government was widely regarded as corrupt and incapable and the famines and floods were seen as an indication that a decadent emperor had lost his mandate of heaven." (
http://en.wikipedia.org/wiki/Yellow_Turban_Rebellion)
There have been other uprisings since, but that one's the prototype -- and the Chinese have long memories. The government is as aware of this as anybody, but paradoxically, their attempts to stay in power by buying grain on the world markets is only likely to destabilize other marginal regimes.
http://www.upi.com/Top_News/Analysis/Walker/2011/02/14/Walkers-World-The-new-Egypt-needs-food/UPI-21451297683420/?dailybriefWith world food prices hitting highs this month, the situation is about to get a deal worse thanks to the latest report of what the official Xinhua news agency says is China's worst drought for 60 years. Xinhua added that Shandong Province, the heartland of Chinese grain production, was facing its worst drought in 200 years unless serious rains come this month.
Reports from witnesses say the land is so dry from Beijing south through the provinces of Hebei, Henan and Shandong to Jiangsu province and Shanghai that trees and houses are coated with dust -- the topsoil that has blown off the drought-parched farmland. . . .
That is the real concern for the threatened regimes of the Arab world. Once China with its massive sayings of almost $3 trillion in cash starts to hit world food markets, few other countries are likely to be able to afford to import the grain needed to fend of riots and even starvation. Hungry people have little patience and few options and if the United States and Europe want events in Egypt to unfold in an orderly and peaceful manner, food supplies may be the key.