It's everybody's favorite interviewing technique: Ask a fairly esoteric question that you are thoroughly familiar with and sit there and feel superior while the candidate struggles to get to an answer you will accept. Three kinds of candidates do well: those who are smarter than you are and spit out answers that surprise you; those who have heard the question and act like they're thinking it through for the first time; those who are unfamiliar with the area but have a personality you find congenial, so you coach them to a solution. In the end, it's all about ego.