predcon: I know what it means. And the Starcraft 2 CE's probably came back because some whiny 12 year olds (in spirit, obviously. They couldn't place orders if they were actually 12. Although that story with that English kid using his mum's card on XBL has me wondering) found out about the DRM and cancelled their orders.
Canceled orders might have something to do with it but I also bet they get a certain promise of getting so many copies, but then closer to launch their allotment might go up.
It's a really good sign the PC version sold out so fast... we might see really strong PC sales for this game. I bet a lot of people like my father-in-law are old-school PC gamers who don't buy much anymore but will come out of the woodwork for more Duke.
Edit: And now the Xbox edition is sold out as well on amazon. Gearbox made a very good choice in getting the rights to this.