[Part of my MMO Design Folder]
Much like a shepherd herds sheep, MMOs have become too efficient at herding players.
Do you find yourself drawn to exclamation points or question marks or other strange sigils on your map when you play an MMO? That's the game enticing you to go where it wants you to go. While it is convenient, I wish that there were still the unmarked quests that require players to decide for themselves what path to take and who to talk to. If you come across someone who asks you to do something then you should pay heed to their directions because there won't be a highlighted area or quest marker to assist you on where you need to go. That should be up to you to work out.
Your quest journal should also record who gave you these quests and where they are so you know who to go back to without relying on some magical orbital relay satellite and your mystic GPS. The less games let you use your own head the worse it is for everyone I think, especially as people get more and more used to being robots running from point A to point B to check off another in their laundry list of tasks to do. Might be hard to get rid of the laundry list unless you're playing in a sand box but the game should at least stimulate your mind to solve some things out on your own, otherwise it's just casting "polymorph to sheep" on us, and it's working.
Also I foresee that while a "shared" system of marked and unmarked quests would be ideal, people will just complain that the unmarked ones are "broken". I suppose this would require an all or nothing approach then for consistency.
The irony in this is that in my own NWO Foundry quests I've found that people expect to be led by the nose to their objectives. The minute I drop all markers and make it open questy type, my review score drops. It's a little frustrating to say the least.
Update: Looks like I'm a bit late to the table with this as the Extra Credits channel recently did a pair of videos talking about Quest Design and they are definitely worth a watch. :)