You dawg I heard you like relying on the cloud for backup, so I backed up your cloud data on the cloud so you can rely on the cloud while you rely on the cloud.
Another service that could be really helpful for this problem would be one that would just automatically burn your DropBox account (which ideally had copies of your other cloud-based data) onto DVDs and send them to some location at some interval for automatic cloud-based offline backup. Not sure if you can automate the mailing part, though, and I would worry a little about ensuring that people get the right data.