Offical Survival Multiplayer on a single world.

Using an unmodified Minecraft client, everyone could join at the same time in the same world.

Now, unlike realms or servers, which are meant mostly for specific types of players, This could be open to everyone or pay to play. It could be fun if thousands of players (or even more) were in the same world.

because a high form of griefing may happen near the spawning area. I suggest that players spawn at random locations, and to find other players, you can walk around the world to find people. When they join, friends could spawn nearby when they start. 

There should be some rules for not hacking, exploiting bugs, and restricting chat (or nearby chat). But other than that, I think it could be regular survival as much as possible.

What do you guys think? I think this could be fun.