I saw this type of addiction hit a few people, one in an extreme way. Most games allow you to see how much time you have spent playing the game. A person that used to work with me picked up Dark Ages of Camelot, and began playing the free trial (30 days). At the end of that time, he looked at the played time, and it totaled 20 days. Mind you, thats not 20 days in that 30 days he logged in, that was 480 hours played in the game. He had used his vacation time for the year to take off from work, and spent it all in game.

In one month, he managed to play a MMORPG more then I ever have. And I started playing Everquest in 1999, quit it for a while, then moved on to DAoC and now Shadowbane. I still don't think I match his time, though I might finally be close after 4 years.