I don't think it is nuts if it is clear in your hiring process. Grockit has you pair for a day for your interview (or they did a few years ago) so you can experience what it is like, and see if you are a good fit. I agree that surprising people with pairing or trying to mandate it on an existing team is unwise, but building a company upon an ethos (to the exclusion of certain personality types) is a reasonable decision.