The South Park episode on World of Warcraft was hilarious, but it's a sad case of "Funny 'cause it's true". Here's a blog post detailing the downside of WoW addiction:
when a father/husband plays a video game all night long, seven days a week, after getting home from work, very involved instances that soak up hours and require concentration, it makes me queasy that I encouraged that. Others include the kids you know aren't doing their homework and confide in you they are failing out of high school or college but don't want to miss their chance at loot, the long-term girl/boyfriend who is skipping out on a date (or their anniversary - I've seen it) to play (and in some cases flirt constantly), the professional taking yet another day off from work to farm mats or grind their reputations up with in-game factions to get "valuable" quest rewards, etc...
This makes generic internet addiction look mild.
In the near future, the self-help industry will realize the goldmine of potential new customers who are trying to break the WoW habit and rejoin the real world. There will be books, groups, recovery programs and possibly even medications that are sold to help these people.