hell, I'll play devil's advocate
We ahve them in Chicago, but it seems that even over recent years they've become much smaller than what they are in SF, and even NY. Personally, I've never had a problem with it (I very rarely drive, and haven't been causght in one) I think the larger problem here is that while some cyclists may be assholes, (riding on the sidewalk; demanding you get out of their way) plenty of them are not. Many of them are forced onto the sidewalk b/c the drivers are so freaking terrible around here. Many have no qualms about running into a cyclist with their vehicle, and for no reason. A few friends and aquaintances of mine have been struck by vehicles, some minor some pretty severe.
This incident in SF, of course, is way out of line. Such unstructured events tend to attract a lot of hard-core anarchists with unstable personality/mood disroders, who simply wouldn't give a ****** about causing some damage (not all anarchists are like this, though. some are quite peaceful, as silly as they may sound to some of you). If these things had a little more organization, incidents like this could be avoided.
although, I do agree with Fobot. I would enjoy seeing a helicopter descend over a swarm of cyclists.