I'm a little paranoid about security and the idea of leaving the house with my MacBook unlocked, leaves a chill over me. As such, for things like Handbrake encodes, iTunes home sharing and file sharing, it presents a little hassle. Is there a way to essentially lock the system, so if anyone were stumble across it they wouldn't be able to log in and have a look round the file system? You could argue that a thief could simply take out the hard drive and look at the volumes of unencrypted data, but we'll assume it's a rather lazy thief. I suppose, as a practical example, I'd like to have a combination of Caffeine mixed with a locked system.