\r\n\r\nThis is typical of the kinds of interview questions we ask around here. Which reminds me - got any favorite interview (programming) puzzles you want to share? We are always looking for new ones.
Though not really used in interviews (our requirements are slightly oddball, so our actual methodology probably wouldn't be useful to anyone else), our lead dev has been peppering us with ideas for a series of quizzes he's writing -- things like "what is this regex meant to match" (often followed up with "what's the bug in it").
\r\n\r\nPersonally, I'm a fan of laying out an actual (or close to actual) scenario and playing the "how would you fix this" card; specific solutions aren't necessary, just evidence of a working knowledge of debugging under fire (like I said, our requirements are a bit oddball; it's not terribly unusual to get a request at noon for something to be developed from scratch and live before 5PM, nor is it unusual for us to get into situations where we have no way to really test something before deployment -- see [link|http://www.jacobian.org/writing/2006/nov/08/breaking-news/|our lead dev's write-up of our election coverage] for an example).