First let me say I am an ex wow-er. And pretty heavy. In the first 4 years of it's release, I had put ~7000 hours into it. That means that of the 4 or 4 1/2 years I had an active account, about 1/4 of my time was spent on WoW.
I think the fact that WoW is a very good game, along with the fact that it essentially has no ending, is the problem. Maybe I worded that wrong. The game isn't the problem, but the fact that addictive personalities (like me) have no automatic release. For instance, I loved Mass Effect 2 a lot. I played through it twice and pretty much neglected all other parts of my personal and partially my professional life to complete it the first time. But then it was over, and I blabbled about the game to my friends for a while, and then it got swept under the carpet. For someone like me who has potential to be self destructive, WoW is pretty much kryptonite. It's a great game, with a lot of interesting things to learn, a good community (sometimes lol), and a world that evolves at a fairly fast pace.
I've played other MMOs and currently am playing one (Global Agenda) but no other has had the effect that WoW had on me. Single player games yes, but like I said, they have a definite ending.
I think addiction is an accurate word. I know people who would play Halo 2 online always. They would cancel our hockey games, or not come out to a concert, or pretty much avoided anything that wasn't Halo 2. Similar to me, if I was home I would be online. If I was not online I wished I was. I thought about it all the time, always preoccupied. My hygiene suffered, my health suffered, my social life suffered, my relationships suffered. Regardless of all the negatives I would always have the disposition of "oh well, I'll just play more Warcraft". I haven't played it in a long time but I feel like I kicked a habit. If I see my friend playing it, I start to get what I can not explain other than a craving. The same way some ex-smokers can't be around someone smoking. I have an inexplicable urge to redownload all the content and load up, but luckily I have the self-control these days to say "no"
Anyways really interesting article, I liked both the first piece about your personal experience and this one.