This is real 'back to basics' stuff but the issue is how do you figure out who will be a good cultural fit in an hour long interview where nine times out of ten the person is going out of their way to impress you anyway.

The final paragraph really nails it. A candidate will fulfil the stereotype of an interviewee when in an interview scenario, meet them at a hacker meet-up or even for an informal coffee chat and the candidate will feel less obliged to act like your potential employee and more inclined to be themselves.

It's just as important for your potential employee to like you as it is for you to like them so you have a reciprocal duty to try and be yourself when meeting a candidate. Formal, stuffy interviews tend to generate formal, stuffy conversations.