Pretty soon we'll have game economics courses in school
About the topic however, I think there's more to it then game changes. They did indeed make drastic changes, but they also had stiff competition from Blizzard's WOW. I distinctively remember reading about gamers flocking to WOW in hordes. Blizzard learned an invaluable lesson that day about MMO's as well. I would wager what Sony did was nothing more than a desperate attempt to increase their subscriber base. However, new gamers flocked to WOW so instead of attracting new subscriptions, they just alienated their existing subscribers and went home with nothing. I would say that's a bit of a gamble either way you look at it. Be happy with what you got or try to breath life back into the product.