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 &amp; 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