Comment 4 for bug 436724

I suggest that if someone sets themselves up to log in automatically, the "Lock Screen" command is insensitive by default.

Then, if it is possible to get a User Interface Freeze exception for this, I suggest that in the "Users and Groups" settings, the bottom of the "Password" section for your user account should have a checkbox, "Allow locking the screen (requires password to unlock)". If you are using automatic login, the checkbox should be unchecked by default, otherwise it should be checked by default. If it is checked, the "Lock Screen" item should be sensitive.

In the long term, the various security settings should be consolidated into a single Security control panel.