Mercurius
Legend
Edit: I think the difficulty here is, unless people have played WoW pretty heavily, they're unlikely to "see" this. Someone playing WoW a few hours a week isn't really going to feel his imagination is being taken over or what-have-you, and he'd be right not to feel that. It's unlikely that many people who even post here have really experienced the effect for themselves. I know that, when 3E came out, if someone had told me an MMORPG like EQ could do this, I'd have said they were full of it. However, experience dictates otherwise.
Good point. I've never played any computer game "heavily," but I've had some TV and internet marathons that I've experienced this. One thing I've noticed is that as a writer of fantasy fiction, my imagination works best if I haven't been watching TV or on the internet prior to writing. I usually need to "cleanse the mechanism"--go for a walk, look at the stars, read Proust (just kidding on that last one).