I have a question about iCloud, hope you can help me with that.
I have read the iCloud documentation for several times, and what I got from that document is iCloud will not update the app's Documents folder to iCloud server unless the app has configured iCloud Entitlements. But, I always see some blogs keep saying that iCloud will automatically sync files in Documents folder of all apps in the device. I don't think iCloud will do that, I mean there is only 5GB there in iCloud server.
Can anybody tells me if I am right or wrong? Will iCloud sync files in Document folder of all apps? Thanks.
iCloud will automatically backup all the documents directories for all apps on your device if you have iCloud Backup turned on in settings. I believe this is off by default.
Apps that implement iCloud APIs additionally can have real time syncing of their own apps data (preferences, database and documents). This is separate to iCloud backups as it is always running, whereas an iCloud backup might happen once per day if you're plugged in and on wifi.
I disabled iCloud when upgrade my iPhone to iOS 5.0, just now I turn on iCloud and try it myself. And the answer to my question is I am wrong, iCloud will upload files in Document folder for all apps, but user can turn it off for specified app.
来源：https://stackoverflow.com/questions/8752513/will-icloud-sync-the-files-in-document-folder-of-all-apps