All this tells me is that tech interviewing is horribly broken. What we have here is a story of a guy with a little bit of experience who has (if his story is true) successfully learned how to game the interview systems at dozens of startups. If you interview people, this article should terrify you. You can argue that it isn't "gaming" if the guy turns out to be a good employee, but that's wrong. If he can trivially game the system, so can anyone else with the ability to go to dozens of interviews and remember questions.
There's a fix for this problem: make the interview about more than the answer to the stupid question. If the candidate answers your question a little too quickly, ask something harder. Chase down a detail. Pick an experience on the resume (and not an obvious one), and dig as deeply as you can. Good candidates know the details. Bad candidates don't have details you can chase.
If you're interviewing correctly, no candidate should be able to come in and snow you with some regurgitated C code from previous interview experience, because you'll be able to out-flank them at every attempt to cough up a line. Unfortunately, there's a corollary: you need to know the subject better than the person that you're interviewing. If you don't, you have no hope of screening for good people.