Yes, minecraft and second life do a decent job but at the cost of stripping away any real plot or purpose. They turn into basically "Online Social Games" in a sense where the entire purpose of playing them is basically just the people. My ideas are all revolving essentially around these issues in mmorpgs.
Old republic is doing a good job with storytelling but of course can also not afford to make any player feel all that special because everyone is going through the same fixed storyline that cannot adapt dynamically to the conditions in the game.
What I'm talking about is a purposed history of the world which drives events in a dynamic, mostly procedural way. Here's a super minor example I keep coming back to...
Trade routes between towns are supplying a war effort. Many rpg's would involve things like "go fetch me X wood from the forest nearby so we can rebuild the bridge and get supplies rolling!" but because everyone has to be able to do that quest, the bridge is then destroyed again if you make a new character (instanced 'timelines' which separate players, make the world feel less interactive and can make playing with friends difficult). In this example you could have the two sides of the war effort either wanting the bridge to exist or be destroyed. Noobs on each faction would have the option of helping to re-build the bridge. No single person can feasibly rebuild it on their own (If they do put in large amounts of effort there would be extra rewards, perhaps the bridge named after themselves, etc. Just small things to make players who put in the work feel like they made an impact). While the bridge may end up destroyed at some point, it's due to on going player interaction, not due to a pre-scripted "repair/destroy the bridge" quest.
This is a TINY example but it brings up a lot of possibilities. Once this bridge is restored, it allows for better trade routes... This can allow persistant NPCs to roam, move to a new city, expand that towns size, shops or features or possibly even found a new town where players can then help bring resources, buy/sell goods, expand trade routes, build defenses, clear PVE elements from the area to win respect in the community. This all involves dynamic procedural content generation and is basically a effort/reward feedback system to encourage people to care about not only the NPCs but also the game world in itself. For putting in the effort they get increased rewards (both physical and bragging rights). If, for example, I put a huge amount of effort into a town, I protect it from bandits, bring all my goods there to buy and sell, build my home there, help them with defenses... the town might end up giving that player their own holiday, name city buildings after them, etcetc.
Obviously all very generic, broad concepts but that's the type of stuff I'm trying to break down into its smallest components and brainstorm on how to make these things feasible.