We use Google Cloud Storage Coldline as our backup file storage. Synced using rclone (rsync for cloud) nightly. The cost is next to nothing. IIRC, ~3TB stored for $25/mo.

Oh even if DO offered an S3 competitor, i'd still have them going to S3 as well. I'd just have them also going to DO's solution, so restores would be MUCH faster, and wouldn't cost an arm and a leg.

And to double the single-points of failure? Now your "stuff" is only alive if both the virtual machine(s) are up, and the object-store is accessible!

What do you mean? It's not like if your object store becomes unavailable your database sending it's backups there will suddenly stop working.

Indeed, but if you're hosting user-images on S3 and they go away your site is broken.

That might not be a big deal, or it might mean your site is 100% broken. I can't guess, but I'd assume since you went to the effort to setup a store you need it in some way.

(No backups? Of a database? That's one power-cut, or hardware failure away from complete data loss too!)