This would probably be a VERY hard thing to program, but may well be worth it in the long run.
The way I see it is this:
New player has NO idea how to get through a quest, and is reluctant to just hop in and try it out for themselves. Well if there is an active group going through the quest, a "spectate" option will be available at the quest entrance. This would let a person enter a quest as a ghost (invisible to the 6 people in the quest) that could not interact with anything, could go through any door that any player has already been through at least once, and could follow the group around seeing what strategies are used in the quest.
What do you all think?