Minecraft Realms, Mojang's server subscription service for Minecraft, is now live in North America. The service was conceptualized as a way to assure parents that their kids would play on safe servers. It costs $13 per month for a subscription to your own self-contained world.
The announcement states that servers will always be available, and if something goes terribly wrong in your server, you can restore it to an earlier state. It's invite-only, but if one of your friends decides to wreck your perfect palace you can undo that easily. Realms is only on PC for now, but Mojang states it will be coming to "other formats" sometime in the future.
Mojang also recently detailed its upcoming Minecraft 1.8 update, which will give much more precise controls over the world creation engine.