Comment 24 for bug 48734

I think you guys should take a look at the permissions on your OS X home directory, you'll be surprised :)

Our security team FAQ has instructions on changing the default behavior for home directories:
https://wiki.ubuntu.com/SecurityTeam/Policies#Permissive%20Home%20Directory%20Access

That being said, applications should already be storing private data in your home directory with restrictive permissions. If you spot an application that stores private data such as email or browser history with inadequate permissions, please file bugs.

Our official solution to keeping user data private is to use home directory encryption by checking the "Require my password to log in and to decrypt my home folder" option during installation.