Since you previously had synced with the computer, it might recognize it's backup keys and therefore let you try again and again. FBI didn't have any backups to go on, right?
I have synced with the computer before, but I needed some disk space a while ago and deleted everthing related with the iTunes. So, do you think those keys were backed up on my computer?
I've deleted iTunes assets on "~/Library/Application Support" and "~/Music/iTunes". Also, before doing that I've deleted all the backups I had on "iTunes > Preferences > Devices".
It would be awesome if there was someone out there who could test this. :)