So an average WoW player plays what, 2 - 4 night a week? Let's say 3 nights a week for 3 hours each night, that's 9 hours a week. Multiply that by 9,000,000, and you have 81,000,000 man-hours wasted every week.
That's almost 10,000 man-years (9240 to be exact) wasted every week on WoW. That's something to think about!