Tarsnap costs 2-3x more than Amazon S3, and S3 is already several times more expensive than it should be. What is the advantage of Tarsnap over S3 and one of its many clients?
Tarsnap enables you to separate out the ability to write/read/delete. So a compromised box could at worst be used to inflate your tarsnap bill but not to wipe out all your backups.
Thanks for the follow-up.
I'm launching the Rest Backup beta next week.