i don't want to pay someone else to host a copy of my data when i have perfectly good encrypted backup mechanisms in place. i want offline copies of it to store, look at, modify, copy, etc. whenever i want, and the fewer companies that have access to my private data, the better.

also, many of the reasons backupify.com cites for needing backups would also apply to their own s3-backed service. "hackers", storage failure, human error, TOS violations, accidental account lapse/termination, etc.