Ok...so the idea came to me from picturing old Taverns in small communities where people meet..and from time to time groups of strangers (Scouts/Guards/Rogues,etc) drooped by and sat at a table,talking about their stories/adventures.
Many people where attracted about their stories ,what "beasts" they've meet on the way,what ruins have they found and wheat items did they heard about.This type of discussions are essentially quest.
Considering the open world of ESO and the approach it takes in exploring the world and finding quests the "Learn about Quest" System comes into place.
Lets say some players find different unique quests that are hard to get,by reaching a deep level 4 cave,or deep exploring of a territory,or they are founded by luck from an wondering NPC.
If the user meets players in town and they have completed different quests then him, a system of Learning about Quests should be introduced,allowing him to learn , by interacting with the other player, where to find that NPC to start that Quests ( uncovering the quest giver on the map).
This will strengthen the social in game bounds,strangers might try to interact each other,being curios of the quests the other player found.
The actual Learn about a Quest system is at the will of the players if they wants to share the location of the Quest Givers or not.
Note that a small icon can be displayed near the player who has new quests done or be displayed in the info panel. Or a ON/Off System can be implemented that the user can activate or deactivate if he wants to see other users that have new quests that are unknown to him. This doesn't mean that the user can check the quests that the other player have for him, just an info that the user has done other quests that haven't been discovered already by him.
Note that a quest level limit can be added for example a level 10 player can't learn about a level 20 quest.
I know it might sounds like WoW quest sharing but the users don't have to be in the same party to share the quest and the user can see who has new quests that can be learned about and are appropriate for him..
I hope this suggestion is helpful in some way in the development of ESO and opens new ideas for the right people.
Bets Regards