I think the biggest problem is the lack of control. If someone makes a mistake, has a seizure, loses control etc, and crashes into a cyclist, the cyclist has less 'protection' around them.
According to [0], 22 people were killed on bicycles in 2012. Compare that to 81 for an ordinary car, 31 pedestrians and 11 on a motorcycle.
Accoring to [1], bike rides make up 16% of all trips in Denmark, but only 3.6% of the actual number of kilometers travelled (which isn't really surprising). According to [2], car rides make up 46% of all trips.
So even though the number of car rides are only almost 3 times bigger than the number of bike rides, the number of fatal accidents are actually almost 4 times bigger.
Edit: Oh, passengers aren't included in the 46%. They make up 12% according to [2]. So my last point isn't completely valid, its more like they're equally fatal.
My calculations were based on the number of trips, not the amount of kilometers traveled. I don't think it's quite fair to compare fatalities/kilometer, as cars obviously travel much further than bikes. You're free to disagree.
Edit: And it's not 3.6% of car kilometers, it's 3.6% of the total distance traveled, whether by car (as driver and passenger), bike, public transport, walking, motorbike and so on.
2nd edit: And for clarity, accoring to [2] above, car rides (driver + passenger) made up about 75% of kilometers traveled in 2012 in Denmark
Bicycle: .039 fatalities per million miles Car: .016 fatalities per million miles
http://www.bellboycott.com/cached/www.kenkifer.com/bikepages...
I think the biggest problem is the lack of control. If someone makes a mistake, has a seizure, loses control etc, and crashes into a cyclist, the cyclist has less 'protection' around them.