Heh, Jah you seem to over simplify others perspective. Obviously its more that simply adding another HDD to the mix, but its not too far from truth for whats involved. The character data is simply stored on the server archive. This is limited (not usually by memory, there is likely plenty of space on those HDD's ) But rather by the ratio of what they believe 'max vs active' will be. They want to not degrade the experience for those who are already logged in. They simply should have increased the max amount of active connections. Adding more allowed active connection to the world is possible they just didn't really approach it from that aspect it seems. Instead they relied on 2 new world creations to give more options for people to go to to solve the problem.

If there are too many people trying to log into a world, then let that be the players choice to tough it out and wait in queue etc...but to not let the players even TRY to belong to a world is really a poor choice.