A bicycle can't accelerate out of the way as readily.
Due to the generally lower speed, exposure to redlight/stop sign runners is a lot higher.
There there is the typical rider who thinks he is immune to stopsigns, lane and even direction restrictions. I imagine that the idiots who rid in a group 4 or 5 across instead of singlefile blocking traffic lanes whilst riding 10 - 15 MPH freustrate some people to the point that if they don't get themselves run over, they will cause someone farther down the road to be smashed.
Then, of course, there are the fools who pedal very slowly and wander all over the place because they are too busy yapping on the phone to pay attention.
