The simplest mitigation to this is to store your primary systems in a different location to your backup. This way the likelihood of both your primaries and your backups becoming unavailable at the same time are significantly reduced.
I don't see how that mitigates the issue at all. The case I'm talking about is when your primaries totally bite the dust. It's obvious that a backup system shouldn't be in the same physical location as the primary system.
The issue I'm referring to isn't about lack of availability of tarsnap's backups, it's that it's very slow to restore backups if you need to do a complete restore (rather than just grab a few accidentally trashed files).
