If you were hoping to sync both work-related and personal i Tunes Store purchases to a single device, for instance, you're currently out of luck.
The problem could get far worse once i Cloud launches, which is expected to happen in the next few weeks.
It could also be that you want to share your files with your spouse.
Users may have multiple Apple IDs for a variety of reasons, such as separate accounts for work and home use, or multiple Apple IDs used by a single family.
Mobile Me users can also use their Mobile Me accounts as an Apple ID.
That's not a problem on your computer—you can have multiple i Tunes accounts authorized on a Mac or PC.
Unfortunately, you can only associate one Apple ID with a particular device in any 90-day period for i Tunes in the Cloud.
When you link an Apple ID to your i Phone, for instance, any apps, songs, and i Books you buy from your computer are automatically downloaded to your i Phone (and vice versa).
The problem comes in when users have multiple Apple IDs.
With Home Sharing enabled, you can copy copyrighted content between up to five different computers.
Content without copyright management can be copied as often as you want. Click “Advanced” on the horizontal menu in i Tunes and click “Turn On Home Sharing” to enable the Home Sharing feature on this computer. Click “Home Sharing” under the Shared heading on the vertical menu to display a list of Home Sharing connections available on your network.
One developer currently testing the full i Cloud beta confirmed to Ars that juggling the two accounts causes issues with i Tunes syncing, and in some cases songs are disappearing from the library on his device.
This has been independently confirmed by other developers as well. Apple IDs "cannot be consolidated," according to Apple, and it's not possible to change your current Apple ID to match your Mobile Me account (trust us, we tried).
Apple was not able to respond to our request for more specific information on the Apple ID issue, but we suspect that coming up with a workable solution is a top priority.