I've heard of that. I think most people who create things are required to spend a lot of time in their heads. Like any behavior, in order for it to become a "disorder" it must cause disorder in one's life (or other people's lives). Someone might daydream 8 hours a day and still manage to live a healthy life style if that daydreaming time is balanced with the other aspects of life. Also, many creative ideas arise from aimless daydreaming. I think most people are too obsessed with feeling productive. A little more daydreaming might make us more relaxed and sane. Work for work's sake generates nothing but cultural pollution. I think I'm always fluctuating between trying to navigate reality and daydreaming. Daydreaming is happier.