From the Chronicle:

...a confrontation between the two sides escalated to a physical violence, when a San Francisco man named Kevin Johnson, 48, walked into a crowd of torch supporters and began yelling, "Communists!"

So SF is a little bit crazy about most things, so running a torch through town in support of a very public world event being held by a country with a ton of historical and ongoing abuses of human rights was always going to be a circus. Also, check out the route: apart from Europe, it's basically 1 stop per continent before you get to South-East Asia, where it hangs around for ages. Everything about this torch is a political statement, so making counter-statements by blocking the torch is completely justifiable.

A lot of people are asking: why is China bothering with the torch at all? It's not like it's a surprise that it's being protested. In fact, why did they try for the Olympics at all? Weren't they prepared for the huge influx of protesters and media coverage?

I think the key thing to remember is that China's leadership is not monolithic. There are some within it who want to see China open up and chill out and give its people more freedom, and others who want to maintain the status quo. The conflict we're seeing over the torch and the Olympics is mirrored within China itself.

The most hopeful sign that China will one day resolve its huge environmental, social and human-rights problems is the very fact that it's willing to put itself on the world stage with the Olympics. This is not the inward-facing empire of old, but a deeply flawed nation still just beginning to engage with the realities of a global society. And the fact is that China is just too big for that process to be one-way: we're not about to mold China to some hypothetical global norm, they are about to Chinese-ify the world too.

So let there be protests and controversy, but let the Olympics go ahead. We -- the world and China -- had to start learning to live with each other sometime, and protests are better than not talking at all.