i think it's just the combination of the addictive nature of mmo's and the already established fanbase of warcraft. i think that's all there is to it really! a lot of people were already mildly invested in the warcraft series, so here comes the same stuff in mmo form and now you're playing a game where every time you're about to complete something you end up starting something else and so you never feel like you've got a good stopping point and you keep playing for the rest of your life.
that's just madness. particularly considering the fact that final fantasy 11 is kinda the same scenario, but most everyone eventually woke up to the fact that it isn't at all fun. kinda is the key word there, i guess, because at least you can be vaguely productive in wow. you can play for hours in final fantasy 11 and not accomplish shit. maybe that's the key difference there?
i dunno, it still perplexes me. i've known some relatively intelligent people play this game for years. i don't think you can do that with a game if you find it revolting. maybe i just don't GET wow.
still don't know how people don't get immediately turned off by how ugly of a game it is. usually i'm not awfully picky about that, but wow is just a fucking unpleasant thing to look at.