Recent updates from Apple caused the /Users folder to be hidden on many users’ Macs. At first, it was thought that this was caused by the OS X 10.9.3 update, but it turned out that it was caused by the iTunes 11.2 update.
Apple has released iTunes 11.2.1 to fix this issue. As Apple says in its notes:
Upon each reboot, the permissions for the /Users and /Users/Shared directories would be set to world-writable, allowing modification of these directories. This issue was addressed with improved permission handling.
Apple is describing a security issue related to permissions, but this still does not explain why the folders were hidden; and only if you had Back to My Mac turned on.
Yet it was clear it was a bug. A lot of people went all conspiracy, saying that it’s another step in the iOSification of OS X by hiding another part of the filesystem. The mere fact that it didn’t happen to all users made it obvious that it wasn’t intentional.
In any case, grab the update from the App Store, and we can put this one behind us.