That's a question the Freakonomics blog asked recently. My short answer: probably not. They disagree. They quote a study that states that:
Per kilometer, cyclists are 12 times more likely than car drivers to suffer a fatal accident
But that doesn't answer the question they asked. If you remove children from consideration that ratio goes way down (the study considered all cyclists). In addition I suspect it will go down if you remove inexperienced or recreational cyclists. If you were to compare bike commuters to automobile commuters I think you might find a fatalities-per-kilometer ratio for cyclist that is as good as, or even better than, the one for drivers.
Some numbers. In 2005, cyclists made up 6.3% of all traffic fatalities in the District. In 2004 it was 7%. In 2003 it was 0%. In 2002 it was 2.1%. In 2001 it was 2.9%. I believe in 2006 it was also 0%. That makes a 6-year average of 3.05%. Without knowing who constituted that group of cyclists you can't eliminate any for being too young or inexperienced so let's stick with the number. According to the 2000 census 1.21% of cyclists biked to work. Of course that number is out of date and poorly gathered (those are people for who biking is the primary means of getting to work). So, while it seems cyclists are over-represented in the numbers by a little under 3 times, it's certainly nothing like 12. And I think with better data, you see results that are even less scary. Of course, I'm not considering it per kilometer either.
One thing they do point out is that the added risk of injury (if there is one) is somewhat counterbalanced by the added health benefits of biking.
On the other hand, a Danish study found that people who do not bike to work suffer a 39 percent higher mortality rate than those who do.
The post has some good links One of the links was to a Times article that mentioned
A journalist who regularly bicycled to work in Washington was killed when he rode headlong into the door of a truck as the driver opened it.
It also has a nice graphic, but it also has some things you might disagree with or find overstated.
Further injuries and deaths result from cyclists who ride illegally on the sidewalk and mow down pedestrians.
But it includes this nice stat (though as a way, oddly, of showing that cyclists are sometimes to blame)
One study attributed 60 percent of bicycle-motor vehicle accidents to the drivers and 17 percent to cyclists. But another study of crashes involving children on bikes found that 80 percent of those accidents were the fault of the bicyclists.
Which backs up what I was saying about kids above. Another great article is this one from 2006
“With the subway,” Mr. Ford said, “you’re literally in a tunnel. When I bike, I see faces. I see storefronts. I’ll stop to visit someone. I’m engaged in the city.”