This is why I don't do Critical Mass much anymore. Cyclists' Bully Day.
From SF Gate/Chron's Matier & Ross:
Susan Ferrando, her husband, their two children and three preteens had come to San Francisco from Redwood City to celebrate the birthday of Ferrando's 11-year-old daughter. They went to Japantown, where they enjoyed shopping and taking in the blooming cherry blossoms.
Things took a turn for the worse at about 9 p.m., when the family was leaving Japantown -- just as the party of about 3,000 bikers was winding down its monthly red-lights-be-damned ride through the city.
Suddenly, Ferrando said, her car was surrounded by hundreds of cyclists.
Not being from San Francisco, Ferrando thought she might have inadvertently crossed paths with a bicycle race and couldn't figure out why the police, who she had just passed, hadn't warned her.
Confusion, however, quickly turned to terror, she said, when the swarming cyclists began wildly circling around and then running into the sides of her Toyota van.
Filled with panic, Ferrando said, she started inching forward until coming to a stop at Post and Gough streets, where she was surrounded by bikers on all sides.
A biker in front blocked her as another biker began pounding on the windshield. Another was pounding on her window. Another pounded the other side.
"It seemed like they were using their bikes as weapons,'' Ferrando said. One of the bikers then threw his bike -- shattering the rear window and terrifying the young girls inside.
All the while, Ferrando was screaming, "There are children in this car! There are children in this car!"
Pretty scary. I've done Critical Mass years back about 20-30 times, and only seen much smaller incidents like this when cars tried to shove cyclists out of the way, or drivers got out to start fights.
UPDATE: This event has spread all over the bike/blogosphere, and at SF Gate:
The minivan was behind her as it weaved its way through an undetermined number of cyclists, she said. Then it hit a bicyclist near Octavia Street, she said. He fell to the ground, McCarthy said, and the bike went under the front of the minivan. The driver, she said, didn't stop until four cyclists got in front.
Basically, car/bike confrontations are scary and unpleasant. I'm not a confrontational cyclist, until I get swerved at honked at, or nearly hit. This is the one day a month when the most aggressive cyclists get away with this stuff.
And that's why I don't do Critical Mass anymore. A few freaks -in cars and on bikes- ruin the fun for everyone. If you want to participate, remember, it's the last Friday of every month, in major cities around the world.