Good point, but I would have said the big win with Tarsnap is the zero-effort encryption. It means that everything you send is safe, so you don't have to worry about whether there is sensitive data in some particular DB / directory / logfile / whatever.
Tarsnap addresses the security concern of cloud backup, making it effectively as secure as on-site backup, but this article seems to stipulate that security isn't a big issue with offsite backup.
