Last month a Chinese official in charge of internet surveillance gave notice that mobs of web users who turn on individuals and make their lives a misery will not be tolerated. In China it happens often and on a massive scale, earning the phenomenon the title of the "human flesh search engine".
On Thursday 21 March 2013, the world changed for Yin Feng, a self-described "average guy" who worked as a part-time taxi driver in the western Chinese city of Urumqi.
Just after 14:00 his mobile phone began ringing off the hook. The callers all berated the bewildered Yin, screaming obscenities and accusing him of acting like an animal.
It took a while for Yin to uncover why the strangers phoning him were so upset.
"Finally, some sensible citizens told me a story about me they heard on the radio, or on the internet," he recalls.
Earlier that day, they told him, a driver in Urumqi had rolled down his window to spit on an elderly homeless person lying on the street. Witnesses recorded the first few digits of the spitter's number plate. The information was quickly broadcast by a local radio station.
Thousands then banded together online to track down the perpetrator.