That can't be right. After all, "Backblaze automatically finds your photos, music, documents, and data and backs it up. So you never have to worry."

There are certain file types that are excluded by default, but you can adjust these in BB's Prefs.

(Disclaimer: I'm a BB customer with 70TB backed up with them.)

A disk image is just a file though. Does it do some sort of analysis of files and block disk images somehow?

Maybe you mean that it doesnt do image-level backups by default?

I wrote some code a while ago that gpg-encrypted zfs snapshots and stored them in backblaze b2.. Just because they don't have software that backs up disk images for you doesn't mean you can't make that happen yourself!