Well, there are two types of POD out there. 1) The traditional kind that we all know about and associate with vanity publishers, and 2) Jason Epstein's
Espresso Book Machine, which creates nearly instant books on demand (IE, POD) just by asking. It's the latter one I'm thinking of. Another advantage, which again the big houses refuse to see, is that these POD book machines can be put anywhere, allowing people to pick up books anywhere one of these machines is, and they don't need to be at a bookstore to do it. The potential sales from this are mind blowing. Which, given that, makes you wonder just how dense the big houses really are.