Me and my friend played Runescape when we were in school. It's funny, because it's ruined his life. He would skip school to play Runescape at least a couple of days a week. A few times his Internet went down and he got really stressed about missing Runescape and his clan meetings, etc.
He grew up on and moved to xbox live, which further ruined. He eventually adopted the xbox live lingo and started using words like 'sweet', 'awesome', 'dude' and 'yeah'. It may not sound like much, but it's words that I'd never, ever heard him say before in all our years of friendship.
He's blocked me on xbox live now and avoids me when he can because I tried to convince him to come out with me at the weekend.
It's quite sad, I suppose, but it's funny because he's so weak.
So, I'd stay away from MMO's if I were you.