I've played mmorpgs for the last 5 years or so without a problem - I'm a bit like Yowl I balance real life and games. I have however seen some people that have major problems with it.
I'm in a high end raiding guild, I go to uni, the gym, work, dance classes and spend time with my friends. But I am also a schedule addict
To me scheduling time in for a raid or an event I want to do is no different then scheduling in a study group for human biology or my psych classes.