Yeah, this is what I was thinking. Though I do have backups of my photos/music, in a worse case scenario in which all my drives were lost/stolen/eaten simultaneously I would lose everything. (This would be unlikely, because one is stored in a safety deposit box.) But a service like this would allow for one extra layer of redundancy with minimal downsides.
Create a giant tar.gz file, encrypt it, and store the encrypted file.
Create a giant tar.gz file, encrypt it, and store the encrypted file.