A couple of articles I came across recently:

MMOs Anonymous: Online RPG Addicts Come Clean About Their Habit (July 28, 2005)

Chinese Government Details Plans to Curb MMORPG Addiction (August 25, 2005) and China's 3-hour limit isn't so surprising (August 30, 2005)
Iffy. What does this teach the wanne-play-longer person? That big brother is watching, nothing else. And maybe more time wasted on figuring out how to circumvent this.

MMORPG's in the College Classroom (2003) -PDF Format
Page 11-12 talks a bit about the addiction aspect

Brave new virtual world: Dispatches from the Cyberrian frontier (March 31, 2005)

A World of Warcraft World: 10 Ways MMORPGs Will Change the Future (Aug-Sep 2005)
Don't take this one too seriously.

Life, death and Everquest: A virtual suicide in the popular online multiplayer game is making some fans queasy about their favorite addiction. (November 21, 2000)
I know, I know, a very old article, but it's an interesting look nevertheless. Some things never change, I guess.