I used to play Eve Online, it was pretty fun. Did tend to get fairly boring after a few months though, and a lot of it felt a bit too much like hard work (I was in charge of a 150-player strong corporation at one point - it was far too stressful to be considered fun). But the good bits were really, really good.
@F1ForFun: That was an awesome wall of text. Shame it seems to have flown straight over the intended target's head.