I don't own a Mac yet but will buy a Air in a few weeks. I'm already thinking about storage and backup strategies. Because I've got a lot of big files and the Air rather not that much memory, I'm forced to use an external drive. I don't like cables so it'll be a network drive. As a backup solution, Time Machine (or even a Time Capsule) seems to be perfect. But of course I want to backup my network drive too, without a second backup software. Now, this seems to be impossible with TM? But why?