A very thoughtful post. I especially like the discussion of the difference between sensitivity and specificity

http://en.wikipedia.org/wiki/Sensitivity_and_specificity

(the post uses other words) or in other words the difference between type I and type II errors.

http://en.wikipedia.org/wiki/Type_I_and_type_II_errors

There are so many interesting ways to think about this. Some of us may have Venn diagrams in our minds' eyes, thinking about the set of {all highly competent programmers} and {speakers invited to programming conferences} and just how those sets overlap.

Of course the important policy point here is that we have no idea how much more flourishing of human developed talent there could be if only all young learners had full opportunity to develop their abilities. I think there are probably a lot of diamonds in the rough in communities all over the world that never get picked up, much less polished. Programming communities can thrive by being welcoming to people who are other than the usual suspects just like current programmers. Props to the author for reminding us not to neglect anyone.