On Friday afternoon news began to leak out that a prominent local activist, Tristan Anderson, had been severely wounded on the West Bank of Israel. He'd taken a metal tear gas cylinder straight to the head and made it to the hospital with an open skull wound.

Anderson was a popular local figure in some eyes. He'd taken part in the two year tree-top protest in Berkeley against the encroachment of development on the local area but had spent years before that reclaiming the streets of the city, while finding time to be an unembedded journalist in Iraq.

San Francisco is a very connected place. There are free Wi-Fi points dotted around, such as in Union Square, and everyone has a mobile phone. But on Saturday the news went digital, hitting the news outlets and social networking sites.

The local paper, the Chronicle, carried the news on the top of page three, a site usually reserved for half-naked teenagers in one UK tabloid. In 36 hours around 3,000 people had signed up to a Facebook group on Anderson and a protest was scheduled outside the Israeli embassy in the city for Monday.

Around 200 people showed up and after spending an hour making their displeasure known outside the building they walked down the main streets to a local subway station, shutting down the main thoroughfare in the city for a while. Similar protests are planned for London on Tuesday.

Ultimately Anderson is in the hands of Israeli surgeons but the speed and effort of response has a lesson for us all.

If, in three days, protests can form over a single issue like this then think about the groundswell of opinion forming in review sites over the months and years. The web has made information sharing commonplace. Companies are going to have to increasingly be on their guard from the angry user.

Now it takes a lot to get people on the streets, but there are plenty of people who will write a poor review from the comfort of their chair.

As the police ushered people away at the end of the protest watching them I couldn't help feeling that with this kind of response in such a short period company analysts are going to have to get a lot better at judging market attitudes, because the response can be swift and deadly.