iCloud on Mountain Lion: one account per Mac or one per user?

Solution 1:

That apple ID applies only to the user account that is created during the setup process. If you look in System Preferences, you'll notice the following option called "Apple ID", under a test account I created:

Additionally, when logging into the new test account, I was presented with the iCloud login screen which you saw during initial setup of the OS install on your Mac.

If you restored your iMac from a backup, or installed Mountain Lion over Lion, you will already have access to those accounts without seeing the iCloud setup screen. In that case, open System Preferences, click on Users & Groups, and set up your iCloud account as you wish.

So, one iCloud account per local account. This would appear to be the case on Lion as well.

Solution 2:

One aspect of iCloud can only be active for one account per hardware device. Find My Mac is exclusive - no matter how many accounts or even how many OS installs you run (say booting from multiple OS - Lion externally and Mountain Lion internally), only one iCloud account gets to find your Mac's location.

Apart from that, each account can use it's own iCloud account fully with no restrictions. In fact, one user account on OS X can have multiple iCloud accounts with the qualification that only the "primary" iCloud account gets these features:

• Bookmarks
• Photo Stream
• Find My Mac
• iCloud storage of files and settings

It looks like another answer has covered the Apple ID part of registration (normally this runs once, but you can always re-register hardware by re-installing the OS) and you may elect to use your iCloud account to redeem any software that was shipped with that Mac when it was new. You can do that in the App Store from the Purchases tab.