A recent study reported by CNN says they're not alone. People who play MMORPGs tend to sleep less and spend more time playing than players of other computer games. It may seem obvious, since MMOs are by nature somewhat of a time-sink, but there is undeniably something more to it; any activity can potentially be a time-sink, after all -- so what is it about MMOs that makes people actually sink time?
The answer is up for debate, of course, but one important factor is that WoW's community of players gives the accomplishments within the game a context of reality. The game's goals, dangling in front of us like carrots, would be nearly meaningless if we could only appreciate them in a single-player context, but with a whole realm of other players working alongside us to get them too, they can feel very important. If the choice is between a few hours having dreams you won't remember, or getting a little closer to riding an impressive dragon mount, then certainly sleep can seem boring and useless by comparison.
As they note in the study, this problem is not addiction. Instead they call it "enthrallment:" the power of the game to capture the fascinated attention of players with amazing items, powerful abilities, and most importantly, other people to share these things with. The study's author noted how very little attention the media gives to enthrallment in comparison to the much-hyped dangers of violence in games, as well as the fact that enthrallment in games can have both positive effects (such as awesome group experiences) and negative ones (such as losing sleep).
Do you feel "enthralled" by WoW a lot? Does this feeling of being captivated by WoW seem like a good thing or a bad thing to you? When does it seem like a few hours sleep is a worthwhile trade for whatever in-game accomplishment you have in mind? Or are you at +150 resistance to enthrallment, with the log-out button just a simple click away at all times?