Here's a thought about trying to save people from completely losing worlds if/when file saves become corrupted. Have the system save an A and B file ("B" being the previous save and the "A"| being the current one... i.e. automatically renaming the previous save as "B" before overwriting "A" with the current save). I believe, this is similar what what Assassin's Creed IV does... and it recently saved me from having to restart a game when I had a power failure at a really inconvenient time. When I restarted, the game informed me that the gave save was damaged and asked if I wanted to load the backup. I did and only lost a little bit of progress instead of everything.
In Minecraft, it would mean that if the "A" save becomes unreadable for whatever reason, the system can ask the player if they want to try to load the "B" save instead and only a little bit of progress could be lost. Also, if a person is griefed, they could intentionally delete just the "A" save and then reload the "B" instead and, with luck, undo the griefing.
One drawback would be that, effectively, each Minecraft world would take up twice as much hard drive space as it does now, but it might prevent a lot of tears... and that would be, IMO, worth it.