I think the cleanest, most compelling backup strategies are those employed by RDBMS products. [A]sync log replication is really powerful at taking any arbitrary domain and making sure it exists in the other sites exactly.
You might think this is unsuitable for your photo/music/etc. collection, but there's no technical reason you couldn't use the database as the primary storage mechanism. SQLite will take you to ~281 terabytes with a 64k page size. MSSQL supports something crazy like 500 petabytes. The blob data types will choke on your 8k avengers rip, but you could store it in 1 gig chunks - There are probably other benefits to this anyways.
It works in theory, but usability is almost non-existent with this approach unless someone creates an app that interacts with this database and provides file system-like access to users. Any normal human would be better off with Dropbox or Google Drive.
Almost like GMail Drive back in the day but worse.
You might think this is unsuitable for your photo/music/etc. collection, but there's no technical reason you couldn't use the database as the primary storage mechanism. SQLite will take you to ~281 terabytes with a 64k page size. MSSQL supports something crazy like 500 petabytes. The blob data types will choke on your 8k avengers rip, but you could store it in 1 gig chunks - There are probably other benefits to this anyways.