I found this very interesting article today in The Escapist that talks about the lack of a trickle down effect from WoW. Which is one thing that many people were expecting and hoping for. The trickle down effect that everyone expected was that as players left WoW they would move onto other MMO's.

The expected WoW refugee trickle-down has stubbornly refused to materialize. As a conservative estimate, it is safe to assume that in any given month, 5 percent of WoW's player base cancels their accounts. Where do these people go? Some undoubtedly dive back into the MMOG pool and spread out among the infinite titles floating around, but at 5 percent, that means there are roughly 425,000 WoW refugees milling about every month. But 425,000 people aren't playing new games each month. WoW just doesn't grow the genre.

Check it all out here: WoW's Magic Number.