Researchers for the blog were looking for references to Find My Mac, iCloud, and MobileMe when they ran into something called "Castle." More specifically, they were able to locate strings that say "Complete your Castle upgrade," and "Click OK to open System Preferences and complete your upgrade from MobileMe to Castle."
At this point, it's safe to assume "Castle" will be known as iCloud to the public. Rumor has it that Apple purchased the domain iCloud.com for $4.5 million from a Swedish Webtop and online file storage service that recently rebranded itself as CloudMe.
Why dump serious cash into a domain name unless you have serious plans for it?
The ties to MobileMe suggest "Castle" will be much more than Apple's online music service. It could be all-encompassing cloud storage solution for music, photos, contacts, files, and the rest of your digital stuff.
It makes sense when you consider MobileMe's current retail packaging was recently pulled off Apple's online store and reportedly marked for "end of life."
Could "Castle" and iCloud be one in the same? I'm guessing we'll have a pretty darn good idea in a month when iOS and OS X take center stage at WWDC.