I don’t consider it ZUI if it’s only easy to use because you have a paid sysadmin who installs and maintains it for you — or you end up paying a service provider to manage it. Of course we can solve our system management problems that way. (Or should be able to.)

The key to my proposal is that is has effectively no cost because it uses existing resources at night. It does cost disk space of course but that’s traded P2P. And it has close to zero administrative load even for the ordinary user without a paid sysadmin.

I am aware of many automated backup systems which require setup or paying money.

While there are reasons one might not want to go this far, it is conceivable an OS distribution could come with a backup system like this already turned on, so it is giving you offsite backup without you doing a single thing or paying a dime, unless you turn it off. Backup is one of those things that should “just happen.”

Right now you wouldn’t turn it on by default because people are not quite ready for the disk space cost. In addition, if they don’t choose a secure password for their account (to be invisible you would use the password the OS already demands they provide) they would be taking a greater risk with their confidential data, which again should not happen by surprise. Finally, they might not have flat rate bandwidth. However, we’re getting closer to a world where points 1 and 3 become unimportant, and the security issue would be the only question.