I want to talk a little bit about quests. I'm definitely not the first, so I won't harp on the obvious failings of the typical MMO quest.
There are so many better ways to do things, and of course, I'm here to tell you how. For one thing, you all have to just accept that static questing is sick and wrong and should be quarantined and if it cannot be healed, put down with a spear through the chest. Good.
An MMO should behave as a somewhat natural, living, breathing, world. The NPC inhabitants will have problems ranging from the very small to the very big and everything in between, all set off by their interactions with each other, with players, and with the environment. If the environment itself is dynamic, the NPCs are able to react to it dynamically, then players will be able to have varied, original, and purposeful quests that affect their surroundings and maybe the whole world.
Example time: A pack of wolves has gotten very large from overbreeding and a lack of larger predators (presumably those were killed by skilled adventurers). They need more food and are starting to roam into the village to get it, endangering the citizens. Citizen A now has problem 1 attached to him and if someone is so inclined to speak with him about what troubles him, he will offer a quest. Now Citizen A has given a quest for problem 1 and will not give another to anyone else unless the person he gave it to fails to return after a few days. The player kills as many female wolves as he can find and the population settles back in and retreats to the wilderness.
Citizen B has different ideas on handling the situation, so when the player goes to him, he gets a different quest entirely that should have the same desired effect. He thinks they should just build a wall around the village, thereby keeping wolves from ever getting in. You spend some time helping villagers collect wood, hire some laborers and help build the pallisade. Problem solved, you get some money, fame, and you personally changed an NPC town.
All interactions can be flagged and tracked, and held in an NPCs memory for a length of time determined by how important it should be to the NPC. If Tom Jones happens upon someone he doesn't know that was robbed by Player C, it wouldn't be as important to him as if he himself was robbed. So Tom Jones may hold on to the story and retell it to the next few people he meets, the man who was robbed will likely tell it for a very long time.
Given enough word spreading, a player may get a quest from an NPC to deal with another player, either by getting back what was theirs or just exacting revenge.
This dynamic world scales as well. When the King declares war on another nation, the whole world will spring up with possible quests for either side and for no side. It will be possible to get quests from the king's men themselves with special jobs for mercenaries, or to join the army. Some quest givers may be spies for the opposing nation or counterspies looking to root out spies. Someone may just want the escort of a trustworthy adventurer in dangerous times.
The possibilities are endless and only limited to how much a developer can think of and put into a dynamic quest generator.