We have a lot of good ideas to make quests non-repetitive and so each player that does a quest will have a different experience. In most online RPGs, quest consist of going from step 1 to step 2 - talk to the NPC, find an object, give it to him, he gives you a note with more instructions on it, etc. These usually end up with a lot of high-level characters "camping" the same area waiting for a specific NPC to spawn so that they can kill it/talk to it/etc. This can often be frustrating to the players, especially if the NPC only spawns once every couple of hours.
Camelot alleviates these issues in many different ways, by included an extensive questing engine. First, the steps in the quest can be randomly generated, so two players going on a quest for the same item may not do the same steps, or not in the same order. Second, players on quests will have to fulfill earlier parts of the quest in order to get quest items off of NPCs. For example, if a player has to say a certain phrase to an NPC to get an item, the NPC will not respond even to the correct phrase if the player has not done the previous steps on the quest.
Camelot also has a special Questing Journal that lists the quests that the player has accepted, and shows the steps that need to be taken, as well as the steps that the player has done already. This alleviates the need for tedious note taking and the "what do I do with this piece of pottery" that happens on other games.