For a number of users, the originals themselves were deleted from the iPhoto library package. It was not just a case of the database being corrupted and the files remaining intact.
Repairing permissions is almost never necessary, gives you a false sense of security, and does not need to be done as a matter of course. (The "repair permissions" tool in Disk Utility is rather unfortunately named, as it has absolutely no effect on user data.)
Permission errors typically only occur due to the user explicitly setting them to something they shouldn't (e.g. being foolish enough to use some unfamiliar terminal command they read on a website like Mac OS X Hints) or a software bug that sets them incorrectly. In any case, the iPhoto library upgrade process should have been robust enough to handle them, and Apple alone should be blamed for the data loss that many people ran into. It's ludicrous to blame the user for data loss in this instance.
That should never, ever be necessary! At most, each file needs to be readable and writable by the owner (you) and nobody else. It shouldn't ever matter whether other users can access the files at all; and if they really need access for some reason, it should be read-only.
