Lots of my friends and family received new iPads and iPhones for Christmas this year, and the question has come up a few times, how to go about sharing iTunes accounts, or what is the best way to handle in a family of multiple people.
First, to differentiate: there are two types of accounts we will be talking about here- iTunes Store Accounts, and iCloud Accounts. Both of these are "Apple ID" accounts, but for the sake of clarity, I'll refer to them by these names.
iTunes Store Account -- this is the account you use when making purchases in the iTunes store. A single iTunes Store account can be used on up to five computers (Mac or PC) at a time. This is done by authorizing the computers via the iTunes program. You can actually use the account on up to ten devices (five of which can be computers).
iCloud Account -- this will be the account used for iCloud, iMessage, and FaceTime. Note that it can also be used as an iTunes Store Account -- and if you are a single person using the accounts on your own, the best method would be to have one account for everything.
If you are trying to share accounts between multiple people (husband and wife, mom and son, or a family of several people) then you would want to do the following.
Set up a single iTunes Store Account -- with a password that everyone will need to know. This will be the account used for making purchases in the iTunes store (apps, games, music, etc). That way, if I purchase content, my Wife can also (re)download it (at no additional charge).
Set up a separate iCloud account for each person. This account will be used for iCloud features, such as photo stream and backing up your contacts and notes to the cloud. Additionally, it will be used for iMessage and FaceTime. Each person will need their own individual iCloud Account.
For the most part, iCloud should take care of your backup needs (you can purchase additional online storage if needed, but it gets expensive). You can also sync and backup to a computer you own (and it is a good idea to do so).
Sharing an iTunes Store Account amongst family members makes sense, and ensures you are not purchasing items multiple times. Having separate iCloud accounts, however, makes everything much simpler and avoids complications that could arise when sharing services associated with it (such as iMessage).
If you have any questions, please post in the comments and I'll do my best to answer.
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