If I had 3 person-days of top developer attention aimed at me over the next six hours, I'd make the most of it. I'd find out exactly what it takes to succeed at that company, and if I really wanted to work there, I'd go home and learn those things better.

I think that that's the main reason that it matters that all these guys were in their 20's. I wonder if any have had kids, a family, anything that's more important to them than their work. If I were slated to interview at a company for an entire day, and I knew for certain that I wouldn't be joining them after only a couple of hours, I would without a doubt make the decision to go home to be with my kids.

One thing I would do that this gentleman did not do, however, would be to speak to the principal about my concerns alone before walking out. Seriously, he forced the guy to follow him to the elevator to get an explanation. That's terribly insulting, regardless of the situation. Give the guy a chance to prove your impressions wrong.

I've been on interview loops before and if it's clear that it's not a good fit we cut the loop short (sometimes by the third/fourth interviewer). This cuts both ways - there's no point in dragging the process out for both sides if it's clear what the resolution is going to be.