I think Apple caused a lot of confusion by poor nomenclature. By using the generic term Apple ID, it's not intiuitve you can create different ID for FaceTime, iMessage, etc - while maintaining a shared ID for iTunes.
IMHO, they should used iTunes ID for that ID and used Apple ID for subsequent ID's used for other apps. That would make it a lot easier for people to understand where to share (iTunes ID) and where to set up individual ID's (FaceTime, iMessage, etc.)
Exactly! But better yet, they should have called the new ID(s) just "iCloud ID".