There’s a developer preview of the next Mac operating system floating around out there (so people who build software can have compatible stuff ready to go). A French blog was first to report that hidden deep inside the code are references to something called Castle, which seems to be a code name for a huge new Apple cloud effort. One of the mentions in the code says “upgrade from MobileMe to Castle”. MobileMe is Apple’s existing cloud service, which is well reviewed but hasn’t really caught on. TechCrunch is confirming that this is all about Apple’s new cloud. “Castle” is probably a placeholder name, though. Apple bought the domain iCloud.com recently for 4.5 million dollars (don’t you wish you thought to buy that domain name a while back?).