I am the guy who asks that question on every interview. You can hate on me now!
Let me clarify. I don't expect the candidate to get to the "a-ha" moment at all. I make my expectations very clear upfront so that the other side wouldn't panic. However, I expect to see how the candidate would approach the problem with the right attitude so I could get some insight of his/hers thinking patterns.
I personally wouldn’t mind if an interviewer asked me something in the lines of "how would you build a nuclear plant?", although I have no knowledge on the matter.
Had this conversation with a co-worker yesterday. As much as I love Chrome, they are heading right down that slippery slope. Soon they're going to figure out something better for drawing than Canvas or SVG, and they'll integrate that Chrome only technology. We'll come full circle when they name it VML.
