Apple - Guest login got enabled even though FileVault 2 is enabled and Guest login is disabled

How to disable that “Guest User” from appearing at the OS X 10.7.2 login screen

• Open System Preferences
• Click on “Security & Privacy”
• Click the lock in the lower corner and type in your administrative password to unlock the control panel
• Check the box next to “Disable restarting to Safari when screen is locked”

This prevents the Guest User account from being visible at the login screen both during reboot and at the login screen. Again, it’s highly recommended to keep this enabled for security purposes, but if your Mac is locked down with a security cable or you don’t have any use for Find My Mac, you could disable this and not feel too bad about it.

If you haven’t tried it yet, clicking on the Guest User account gives you this message:

This computer will restart to a secure, Safari-only system for the Guest user.

The reboot process is quick and opens directly to Safari, there is no access to anything else. No Finder, no preferences, nothing.

Source: osxdaily

This appears to be by design.

Keep in mind, the whole drive is still encrypted with File Vault. The 10.7.2 Guest/Safari-only User only has access to / runs off the Recovery partition, not the main volume where your user data and applications are stored.

If someone does login to the Guest User, they have no access to the system partition, and as a bonus, the Mac is findable via Find-My-Mac.