I was under the illusion that a Time Machine backup would do as they claim:

You can set up Time Machine to automatically back up all your important files, including your documents, music, photos, applications, and any other items you keep on your hard disk.

I consider my iTunes authorizations important, but apparently Apple does not. Seems that these are specifically excluded from backups… Removing the “SC Info” line from the /System/Library/CoreServices/backupd.bundle/Contents/Resources/StdExclusions.plist file solved this.

I know I should have de-authorized my machine before reinstalling, and I know you can “de-authorize all” to fix this as well; but it’s pretty disturbing to see iTunes remove all your applications from your iPhone…