In Leopard, you can configure it so that a password is required when waking the system from computer sleep (i.e. close the lid) or returning from the screen saver, but not display sleep. This allowed ...
I have a Mac mini running 10.6.7. I have set the screen saver to be automatically activated after 15 minutes, and the session to be locked a while after that. But sometimes, the screen saver stops ...