As an extension of this thought, its always more beneficial to get an prospective employee into problems they know little to nothing about.

This leads to views of thier basic underlying skill/mind set. Do they turn to the manpages? Hit google? Try to bluster their way out? Throw in the towel per se? Have enough of a basic grasp of concepts to make "edjucated guesses" and provide contingencies for what might alter the situation? Try to get you to provide "hints" to the answer? When the answer is provided, how do they deal with the new info? Do they appear to assimilate it? Try and make it seem as if the question were a trick one, and had the right language been used would have provided just the answer you gave?

At first I thought interviewing was showing how much you know in a particular domain. I guess it is, but I have found the best interviews to be when its almost a game of cat and mouse. Pushing to see what they know, and the confidence level there. Jumping to a topic either completely opposite, or maybe even personal (where ya from? what do you do for fun?), and back to a hard technical topic. Not to say we should scar potential employees, but by the same token we don't want to allow people who know topic A and nothing about B or even how to go about learning B in the door. There are exceptions, but I think they are relatively few and far between.

I guess I should note that this is an approach for mid to senior level, though at a junior/entry level, a certain level of enthusiasm and the ability to link previous questions/topics with current questions would be good.

use perl;