Why does he use two SM57's? Or is it why does he use two windscreens? Well I've always wanted to know this also. I'm thinking maybe they use two so in case one of them has a bad connection, the other one will pick him up. I'll have to go on the site to find the answer.
Along the lines of double micing. When budget permits I try to get actors double miced. They sometimes whine about hiding the transmitter packs. But it has been a life saver on several occasions.