Great article. One thing:

If the attacker, whenever he pulls a red ball out of the urn, puts it back and keeps pulling until he gets a blue ball, the Bayesian "rational mind" will conclude that the urn is entirely full of blue balls. ... [But it's] not approaching the most important job of teachers, which is to figure out why you're getting things wrong -- what conceptual misunderstanding, or what bad study habit, is behind your problems.

I don't know much about Knewton, but it seems like it could address this - at least in some cases - and possibly better than teachers. Knewton and programs like it can keep track of success rates at the individual problem level, rather than the test or semester level. Such data could be used to identify the 'bugs' the author speaks of. All Knewton needs is knowledge of common 'bugs' and what problems they make students get wrong.

This article also recalls to mind , specifically the part where problems are considered to be the fault of the system, not of the people involved and are treated by changing the system, not by criticizing the people.