I'll go with bousozoku here...
"Catalytic converters have reduced the output of carbon monoxide in auto emissions from about 9 percent to 1 percent, but lethal doses of carbon monoxide can collect in a closed garage within 10 minutes, says Richard Lichenstein, M.D., F.A.A.P., associate professor of Pediatrics at the University of Maryland School of Medicine, Baltimore, Md."
Link:
http://atoz.iqhealth.com/Atoz/healthupdate/alert04072000.html
Plus, exhaust systems can rust and leak.
Also, people can and do die from carbon dioxide poisoning (though not from cars AFAIK):
http://www.emedmag.com/html/pre/tox/0500.asp
Also carbon dioxide is now a suspected culprit in the deterioration of coral reefs and shell-forming sealife:
http://news.nationalgeographic.com/news/2004/07/0715_040715_oceancarbon.html#main
So I guess "inherently dangerous" depends on your point of view. Sorry to be Mr. Argumentative here.
I would just be happy if Congress would repeal the SUV tax break to self-employed filers, which amounts to a taxpayer subsidy to the car companies.
I think the hope with fuel cells is that future technology will allow us to more efficiently extract hydrogen. I have heard that the current fuel cell technology indeed is not as efficient as more conventional engines.