I think one of the secrets to the critiquing power of the Story Monkeys is the sheer uninhibited manliness of our interaction.
Watch a group of men interact, especially about something manly, like sports. They talk trash, they poke fun, they egg each other on, they raise the stakes, they compete. They do this all, most of the time, without damaging the friendships that bind them.
The Story Monkeys work like a bunch of men talking about sports. We are direct with each other, we pull no punches, we talk straight, we even mock. And, importantly, everyone takes it and keeps coming back for more. We do this, I think, without being offended. I suspect the reason this works is that we focus on the work product and we genuinely try to help each other succeed. The trash talk is about the game, not about each other. I was not offended when Erik "lost all respect" for my character Bad Bill for his insufficient pimptasticity; he was not in turn put out when I asked -- sincerely, but laughing -- whether he was setting his character Kail up for a gay romantic subplot. Both of us got valuable feedback about what we had written, direct and to the point and immediately highlighting potential reader perceptions. Neither of us left the Story Monkeys.
Story Monkeys, ho!