Keep an eye on the woman on the right, we'll call her Miss Inconsiderate. We were ahead of her when we got to the light at 3rd and Townsend. There was a taxi turning right, so the line of bikes went to the left of the taxi. Miss Inconsiderate came up on the right next to us and stopped behind the taxi. (Also note guy trying to pass the taxi on the right) As we went around the taxi and into the intersection, Miss Inconsiderate muscled her way through a hole too small for her bike, making the cyclist on the left make the decision to either hold her ground and risk Miss Inconsiderate taking her out, or go into traffic in the lane to the left. Luckily there was space to get through the intersection and nothing bad happened.
However after the intersection, Miss Inconsiderate decided she was intent on passing people on the right, coming mere inches from several cyclists to her left and in front of her. To top it off, she ran the red light while there was a car coming into the intersection and pedestrians about to cross.
What should have happened: If you're on a bike, queue up behind other cyclists rather than trying to pass them. Bunching up in the front serves only to make the intersection more dangerous as everyone jockeys for the bike lane on the other side. Also, avoid passing on the right. You could get doored, you could encounter an obstacle outside the bike lane (notice the parking sign Miss I. had to slow to avoid), and you could force other cyclists into traffic. If you must pass, take the lane and pass on the left. Also, don't run red lights.