I thinks spectators should be allowed into the quest areas as part of a group. They would have floating cameras and could follow the party around and see everything a party member could. I can think of a dozen objections and issues without even blinking but I think this feature would greatly increase playability and enjoyment of the game for many, be very enjoyable way to spend time online, and increase and/or retain subscribed members.
Possible features
1. restrict number of spectators per group
2. leader of group chooses who can be a spectator
3. restrict areas cameras could access to the current locations of party members
4. limitations on spectators access to chat
5. limit the level of the spectator to the level of the group
6. spectator must have appropiate favor in the quest and can only view same or lower difficulty of the quest
7. party members would have to agree to allow spectators to to view the quest
There are runs I would like to have seen that for one reason or another I was not in. There was a server wide shroud run by clerics some time ago that would have been fun to see.
*edit* P.S. and ddo would have something no other mmo has.