People in Xiamen have been using SMS to organize a protest against a chemical plant they don't like. See Danwei's excellent roundup of Chinese language online sources.

Also in US MSM sources, The Wall Street Journal and  Reuters among others, and in China Daily.

The last big incident of text message mass-organization that I recall (and there may have been others) was the anti-Japanese riots of Spring, 2005. This seems a somewhat more constructive use. Unless, of course, you're the Tenglong Aromatic PX (Xiamen) Co., in which case this probably doesn't seem all that constructive.

The Wall Street Journal article notes that it was getting harder yesterday to forward the message that organized the mass protest which ultimately took place today (see the photo on Danwei), and that some Internet postings had vanished. There doesn't seem to have been much effect, though.

Imagethief wonders if the government stood back a bit from this case because it was an environmental protest targeting a Taiwan-backed company, two factors that might put this issue within the realm of allowable protests. I note that Xinhua's Chinese language story from the 30th cites public concern over the factory. But as near as I can tell, and unlike the English language China Daily story of the same day, it doesn't say anything about the role of text messaging in organizing people.