Walking out of an interview
My answer on this depends on whether we want to be an emotionally supportive group for people who make a badge of honor out of being socially and professionally inept, or whether we want to give advice which will actually move careers forward.A company which is not a cultural good fit for you, and the employees thereof, can still be very valuable allies.  I would not act to antagonize them absent substantial provocation.  Not being like you is not a substantial provocation.  Most people in the world will, after all, not be like you, and you'll end up not working for approximately all companies in the industry.  That's OK.You've already got the day blocked off in your calendar.  Smile.  Firm handshakes.  Thank them for taking the time to interview you.  Heck, they're giving you free live-fire practice for your next interview, make the most out of it.  You should never say a word of criticism about the company to anyone but your primary point of contact and you should be darn circumspect with how you word it to him.  (I like something along the general lines of "Thanks for your time and allowing me to get to know $FOO_CORP better.  We're really in the same boat: I only want to work at employers where I'd do my best work, and you only want to hire people who'd do great things at $FOO_CORP.  Having had the opportunity to hear you guys out a bit more, I don't think we're a great mutual fit.  I will keep my ears open for you in case any of my friends would be a good fit for your position.")