In that scenario, each device should have it's own iCloud Account. That way, people with multiple devices will share
their contacts on only
their devices and there's no sharing between people.
So far so good.
Do you want to share a single iTunes Library that is associated with a single Apple ID across all those devices? If so, that's exactly how it works.
On the iOS devices, under Settings/Store, the Apple ID there will be used for iTunes Match. On iTunes on Macs or PCs, make sure that Apple ID is the one they use to set up iTunes Match. All the devices, which may have different Cloud IDs, will then share a
single iTunes Match library associated with a
single Apple ID.
I'm not sure it's a mess, but it is not obvious. Basically, Apple markets one "iCloud" but it's really two different ways to use those Apple IDs:
iCloud Account (which is an Apple ID, but it doesn't have to be the same one used by iTunes)
- Contacts
- Calendars
- Reminders
- Bookmarks
- Notes
- Photo Stream
- Documents & Data (iWork for now)
- Backups
Note that you can use that same iCloud Account for @me.com Mail and Notes, which may have been a MobileMe Account (which is different) or even a .Mac account (which no longer exists). This has clearly confused some people with the items above because it's not obvious.
iTunes Store Account (which is also an Apple ID, but it doesn't have to be the same one used by iCloud)
- Music from the iTunes Music Store (redownload and automatic download)
- Apps from the iTunes Apps Stores (redownload and automatic download)
- Books from the iTunes Bookstore (redownload and automatic download)
- iTunes Match
Note that you can use yet another Apple ID for iTunes Home Sharing for Music and Video... but perhaps that's less confusing because it's never referred to as part of iCloud.
