From the New York Times (link):
It began with an impassioned, 5,000-word letter on one of China’s most popular Internet bulletin boards, from a husband denouncing a student he suspected of carrying on an affair with his wife.
Immediately, hundreds joined in the attack. “Let’s use our keyboard and mouse in our hands as weapons,” as one person wrote, “to chop out the heads of these adulterers, to pay for the sacrifice of the husband.” Within days, the hundreds had grown to thousands, and then tens of thousands, with total strangers forming teams to hunt down the student’s identity and address, hounding him out of his university and causing his family to barricade themselves inside their home.
It was the latest example of a growing phenomenon the Chinese call Internet hunting, in which morality lessons are administered by online throngs and where anonymous Web users come together to investigate others and mete out punishment for offenses real and imagined.