There's a lot of narrative in the article but no source of where his risk figures come from.
Another source estimates the risk to be two orders of magnitude higher (http://blogs.discovermagazine.com/badastronomy/2008/10/13/death-by-meteorite/#.VWBSy_ntlBc):
Astronomer Alan Harris has made that calculation. Allowing for the number of Earth-crossing asteroids — the kind that can hit us because their orbits around the Sun intersect ours — as well as how much damage they can do (which depends on their size), he calculated that any person’s lifetime odds of being killed by an asteroid impact are about 1 in 700,000.
The article was per year, not lifetime odds. Depending on the detailed assumptions, I'd eye ball those two numbers as actually quite close, given the inherent uncertainty.
One-in-70,000,000. On average.
"Risk to humanity" is a rather vague term.
An asteroid could actually end all of humanity permanently. Trucks may get a few of us, but are less likely than the asteroid to get all of us at one time.
But if we try to OVERestimate the expected value of the payoff or disaster, what is Taleb's Anti-Fragile really about? As it is about UNDERestimating it.
Throwback Thursday: Are asteroids dangerous? by StartsWithABang: