However some people over Electronista recently reported a bug they found when trying to restore their device using iCloud backup, it generates Apple IDs on their iDevice -- not their own.
Apple's support forum is already notified with the bug, they have promised to work on this issue and the fix will be included in the upcoming iOS 5.0.2 -- that is reported will not be released this week. A video demo of this bug has been posted in Youtube showing how Apple ID's generated and shown, albeit those ID's are not theirs.
Currently no fix to this issue, however Electronista suggests that you can avoid such condition simply by NOT restoring your Device data with iCloud backup service. And go back to the general restoring method using iTunes from your computer. Stick with this method you experience the same issue, until Apple comes up with iOS 5.0.2 to bring fix for this problem.