Classes

A. Ninjas (about 15 of the 100 cyclists I see every evening)
B. Salmon (about 5 of the 100 cyclists I see every evening)
C. People running red lights (about 3 of the 100 cyclists I see every evening)

Reasons

A. I can't see them and when I have a green in the bike lane and someone joins without a light it makes it very hard to see them coming out of a side street (Copenhagen solved this with a fast and slow lane in each direction)
B. Most salmon get out of the bike lane if they're going the wrong way but it's a hassle for the pedestrians and gives us a bad name
C. If there are 4-6 of us stacked at a major intersection and someone pushes their way around to the front of us and then runs a red in a traffic gap it makes drivers hate us. Also, why spend billions of € on infrastructure (we have our on bike lane signal with sensors to trigger the entire intersection) if it's not going to be used properly. If these people get snipped by traffic I won't shear a tear.