UPDATE: So it looks like it was all staged
"A motorcyclist who drove at a group of people demonstrating against the federal health care bill was cited on suspicion of reckless driving and released because investigators did not find evidence he intentionally tried to assault the protesters, officials said Thursday.
Police officers surrounded Jeffrey Dillon, of San Francisco, in the middle of the roadway Wednesday, drew their guns and took him into custody, on suspicion of driving on the wrong side of a one-way street at Seventh and Mission streets, and attempting to ram a number of protesters, according to photographs and videos from the scene.
?He didn?t actually make contact with anybody, either lying down or in the roadway. That was the main factor. If he hit someone, it would be a whole different ball of wax,? said Officer Robert Rueca of the San Francisco Police Department."
Biker cited for reckless driving in SF protest disturbance - SFGate.com