Ideally, our computers should use a system where you never need to remember to save your work at all, it just happens automatically all the time. That's how we work in the real world - you never need to "save" what you've written on paper. Creating it and keeping it are the same thing. Of course, that requires software to be written specifically for that arrangement, but then it starts feeling a lot more like something based on reality, built for you, rather than based on engineering constraints and built to suit the hardware.
If you also have a version-controlling file system with automatic remote redundancy, you'll have a very complete history of everything you've done, and backups are practically subconscious. No data will ever be lost simply because you saved over it, accidentally deleted it or even because of ordinary hardware failure.
Mokalus of Borg
PS - I use Dropbox and Windows Live Mesh to get some of this behaviour.
PPS - But I'm talking about designing Windows around the idea.