> I am sure that the deletion of media files in services like Facebook has never meant to be absolute. Many of my colleagues believe the same thing that I believe: Facebook and other services do not actually delete data, they just mark it as "deleted" and purge it only if they need the space.

This is a dumb conspiracy theory. Facebook has made plenty of public statements that say otherwise, and there's a whole team that works on the system that ensures every trace is erased from disks, logs, cold storage and backups when deleting content.