Quote: "Of these nine classic characteristics, we can imagine people scoring either “nerdy” or “anti-nerdy” on each. If that were true, there’s only a 1/2^9 = 1/512 chance that any given person has all of these characteristics."

Not if the traits are correlated with each other. The chosen binary math treatment works only if the traits are independent, i.e. mutually orthogonal. They aren't -- nerdy traits are strongly correlated, so much so that if you find any five of the nine traits in an individual, you're most likely already done identifying a nerd.

Also, there's a more efficient way to express a fractional probability: 1/a^b = a^-b.