The iTunes 11.2 update has a bug that can make the /Users folder invisible. When this occurs no data is lost, all the user accounts still work, however the Users folder at the root level of their boot drive is hidden. This bug also incorrectly changes the permissions to the /Users folder.

Apple has since released an iTunes 11.2.1 update that resolves this issue, making the /Users folder visible again and restoring the appropriate permission settings.