[phuff]

"If the candidate uses up all of the interview time trying to obtain perfect requirements, we have a problem. In the software development I do, the requirements are never perfect. I don’t demand that a candidate try to create an agile, iterative process on the spot, but I look for someone who knows when to say 'close enough, let’s move forward.'"

I think this is a great reason why most interviewing techniques fail. The interview is not a reliable model of the work environment. This is especially true given the fact that people love "gotcha" interview questions which are essentially brain teasers which require you to know some arcane trick to get the question right.

I have seen great candidates spend a lot of time trying to understand a simple problem in an interview. These are people who under normal working conditions would never waste tons of time trying to get a perfect spec before starting work. But, because of the types of interviews people try and pass over as being "reliable indicators of future performance" candidates get stuck trying to find the trick in each question. If you have a candidate spend their entire interview trying to tease out a spec it sounds like a better indicator of the low quality of the interviewer rather than the candidate to me...

When people start heading that direction in an interview, be sensible and say, "Do you feel like you need a complete spec before going on? I promise there's no trick I'm trying to get you to fix" and you'll get the response you're actually looking for.