I know lot's of 'normal' people that ended up having a borderline problem with WoW, realized they had a borderline problem then got out.
Here's the basic track toward this happening. A person in a fairly stable time environment (i.e. they have a regular and somewhat consistant amount of time they can make themselves available) starts playing WoW. They enjoy the game and maybe play with a few friends, but it's still just a game. This person then joins a guild.
****This is where the gameplay experience splits and may cause issues****
If you join a small fun loving guild that concentrates on 10 mans, things go pretty well.
If you join a guild that is dedicated toward seeing the end game content, you need to make some decisions in your life. I went down this path, as did several others I know. Although I didn't realize that was where the guild was going until I was deep in it (I was in WoW on day 1).
You make 'friends' with people you've never actually met and now you make a commitment to them. You need 25 people with alternates to be on 3-4x a week at a set time. These people need to be prepared by having proper food and potions with repaired gear. So now you've committed to your friends that you will not only play 12-16 hours in raids, but you'll play an extra amount of time so that you can show up ready to play.
This, in theory, is no different really than committing yourself to a 'good' amateur Hockey Team that's dedicated to winning it's division. You put in the time and practice.
The social problems are: only you and others that play this understand (whereas anyone-including non-gamers understand wanting to be 1st place in your hockey league), it is exclusionary in an area that's supposed to be inclusive of your family- your home (so your family just sees the back of your head as you're hunched over your pc with headphones on talking to people you've likely never met), and finally- it takes a larger time commitment then other typical commitments. If you want to see Black Temple, Mt Hyjal and the Sunwell, be prepared to treat WoW like a part time job. There is just no other way to learn the coordination. Pick up people will kill your whole raid.
WoW is great fun if you can stay casual. I don't blame WoW either, just like I don't blame alchohol for the alchoholic. You make your own choices. Therefore I quit. Once you start going down the raid content route, it is extremely hard to go back to just goofing around though.