Scalable M(or not so M)MOG

The problem facing many mmogs today is either to few subscribers (lots) or too many (ultima online, where you can not get out of view of a house). What if by providing a main server and the option for players to create their own servers, you could provide a mmog that could be played by yourself or with 1000 other people? Take dark and light for example (I know...). Because the entire world is player created, the gameplay could easily be scaled (or not scaled if you wished to play in a full world) to work on a 64 player online server or a 10000 player commercial server. The options to mod and play the original game would both be there, with a subscription required only to play on the main servers (the main servers could not even be necessary from a buisness standpoint). I know I would like to play a game where I could create my own private world that my friends could join whenever my computer was running it. The ability to develop and play in a persistent world with the people you know, either in real life or online, and JUST with the people you know would greatly increase the enjoyment and potential of any game.

Please, give me your two cents, as I am a poor man and it has been a hard winter...