Comment 1 for bug 967938

The Guest account does not show up in a search either:

# grep -H -r "Guest" /etc 2>/dev/null
Binary file /etc/alternatives/smbstatus matches
Binary file /etc/alternatives/nmblookup matches
Binary file /etc/alternatives/net matches
Binary file /etc/alternatives/testparm matches /etc/X11/Xsession.d/98vboxadd-xclient:# Start the Guest Additions X11 Client

If the Guest account is going to be hidden in an irrelevant configuration file, perhaps a comment with the name "Guest" should be place in /etc/lightdm/lightdm.conf so folks trying to hunt it down can find it:

# Uncomment to disable the Guest (guest) account
# allow-guest=false

Even better, disable it by default:

# Uncomment to disable the Guest (guest) account
allow-guest=false