A secure, online back-up solution for all my computers that is dead-simple to use on all OSes. And I mean dead-simple as in install a client that by default in

A secure, online back-up solution for all my computers that is dead-simple to use on all OSes. And I mean dead-simple as in install a client that by default intelligently finds the stuff that I might want to back-up (iTunes library, folders with lots of pictures, My Documents, /etc & /home directories, etc.), with the ability to specify certain folders/directories as well. Or since we're dreaming, why not the whole computer? And of course it always runs in the background, never consumes 100% of my CPU or bandwidth when I'm using the computer, is always up to date, and pretty much never bothers me once I've set it up. I don't want to think about back-ups. I don't want my family to have to think about back-ups. My dad is interested in getting an iPod and will definitely purchase songs on iTunes. I want a dead simple setup for him to keep those backed up.