I think it is correct that, without unusual precautions, Dropbox should not be counted as a distinct backup copy for satisfying the 3-copies rule. I've "lost"

I think it is correct that, without unusual precautions, Dropbox should not be counted as a distinct backup copy for satisfying the 3-copies rule. I've "lost" (had to restore from personal backup drives) data from Dropbox due to an error made by their support staff during a mass rollback, which was itself needed due to the Dropbox client interpreting a drive disconnection as a mass file deletion. (This was before they implemented mass rollback through the UI; it's a safer process now.) And this is fine. Dropbox does file synchronization, which means it propagates data loss as well as intentional changes.