The Torontoist brought to our attention the City's release of 2010 data on pedestrian and cycling injuries and fatalities from collisions with motor vehicles (on the bottom of the Transportation Services page).
According to the presumption of fault by the police (which wouldn't be the same as the court's finding of fault), in only 33% of the collisions were the police able to determine that the motorists were driving "properly", with about 12% where the driving behaviour is unknown (for the average of the last 5 years).
If we can use the 2006 census as a reference for mode share, it appears as if cycling is twice as dangerous as walking in the city. While there were twice as many pedestrian/car collisions as cyclist/car collisions; there are about 4 times as many people walking to work as biking to work (1.7% bike mode share versus 7.1% walking mode share). A cyclist, it appears, is twice as likely to be in a minor or major collision compared to a pedestrian. While cycling is overall still a safe transportation mode, we could still do a lot to create better conditions for cyclists so they can at least reach the lesser risk levels of pedestrians.
There doesn't seem to be much of a difference between the severity of injury of those wearing a helmet versus those not wearing a helmet (5% of those not wearing a helmet at a major injury and 3% of those wearing a helmet). From this small sample we could hazard a guess that wearing a helmet may have made a difference but not much of one, at least not such a difference that we could justify going all "nanny state" on cyclists. We can have far greater impacts by placing more responsibility on motorists to slow down and by reconfiguring our streets to prioritize active transportation modes (i.e complete streets).