Dr. Clark Chapman of the Southwest Research Institute Department of Space Science puts the risk of asteroid impacts in perspective:

The average American’s chances of dying as a result of an asteroid impact is about the same as an average American’s chances of dying in a tornado….  the chances of death and destruction by cosmic impact are on the same order for Americans as death by airliner crash, flood, tornado, and other hazards society takes seriously, it is reasonable that the impact hazard be taken seriously. In fact, an asteroid impact is a much more serious hazard, statistically speaking, than many other hazards we have experienced in the last few decades, including death by terrorism, by nuclear power plant accident, by shark attacks, etc. And cosmic impacts – if large enough – are nearly unique (along with nuclear war and perhaps some “Andromeda Strain” pandemic) of having the possibility of sending civilization back into a Dark Age or even exterminating our species…

Yet, the amount of money we spend on asteroid-impact mitigation pales in comparison to what we spend on airline safety, flood and tornado insurance, terrorism, etc. It may even be less than we spend on shark-attack research.

Nevertheless, some scientists, such as Dr. Joe Veverka of Cornell University, still pooh-pooh the threat, which he feels is peddled by “peddled by well-established advocacy groups.”  That is an example of the logical fallacy known as the ad-hominen argument. Merely declaring that a statement is made by an advocacy group does not prove that the statement is wrong.

You can read the full debate here.