Even excluding all the details of tarsnap's design, using glacier for backups has always seemed totally wrong-headed to me for a simple reason: it disincentiviz

Even excluding all the details of tarsnap's design, using glacier for backups has always seemed totally wrong-headed to me for a simple reason: it disincentivizes checking up on your backups, which is a key part of doing backups. No point waiting until you lose your data to realize that your backups had developed a glitch. Add any minimal restoring cost and glacier costs about the same as regular storage -- with a lot less convenience. I honestly can't think of a use case for something like glacier, where storage is cheap but reading/writing is expensive.