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:
When it comes to risk assessment, there's one type that humans are notoriously bad at: the very low-frequency but high-consequence risks and rewards. It's why so many of us are so eager to play the lottery, and simultaneously why we're catastrophically afraid of ebola and plane crashes, when we're far more likely to die from something mundane, like getting hit by a truck. One of the examples where science and this type of fear-based fallacy intersect is the science of asteroid strikes. With all we know about asteroids today, here's the actual risk to humanity, and it's much lower than anyone cares to admit. -- summary from slashdot.