I think that one of the really great selling points of this game is the whole idea that the world is so user-influenced and has such a loose structure. I've noticed that a lot of people have created their own mini-games using dice and whatnot in the General forums, but what if we could elevate that and have real user-created quests?
Here's how it would work.
User 1 could write some kind of quest, be it "Collect 5 Luminous Moonstones" or "Visit 5 Roads That Begin with the Letter A" using Penpersonship and then perhaps an advanced level of Bureaucratic Arts.
Then User 2 would go to the "Quest Hall" and look for available quests. If you don't want to build an actual building, it could always just be a page available for browser-view like Real Estate Listings or Auctions. Once User 2 finds a quest that they would like to do, they select it. It shows up in their Magic Rock listing under some special heading.
When User 2 completes this quest, they gain a little bit of XP and a little bit of money, and so does User 1! This will motivate people to write actual possible quests, not something silly like "Jump up and down for five days." If User 1 wants to sweeten the deal, they can attach their own item to the quest that User 2 could gain if they complete the quest-- kind of like bribery to attract people to his quest listing.
The "Questmaking Skill" would have some sort of limit per game day so that the quest listing would not be flooded with entries, and the submissions would be some kind of "Mad Libs" type of structure so that no one could write anything profane or completely unrelated to the game-- like "Please go feed my dog so I don't have to step away from the computer. 100 Currants." Also, there would be some kind of way that the computer could determine the level of reward, not the users. (Obviously.)
I think that this idea benefits many types of players-- those that like having the structure of in-game quests, and those that are creative types that want to add their own touch to the game of Glitch. And of course, those that want more currants and XP.