Tovec
Explorer
They mentioned including something like that into the DMG. No reason it should be a separate book.
That is like saying EVERYTHING about dragons (or demons, or devils, or undead) belongs in the MM and only the MM. Instead of allowing a draconomicon, friendish codex, libris mortis and so on.
There should certainly be aspects or the bare bones information on how to create worlds, settings and campaigns in the DMG but I agree with [MENTION=2072]Aeolius[/MENTION] that a proper World Builder's Guide might be needed in order to give ALL the information one might require to build, populate and run a world.
I would not mind shelling out the extra money for the core 3: PHB, DMG, MM and then buying a highly detailed book for Campaign Setting World Builders Guide, or whatever they want to call it. I have shelled out more money for setting books in the past and I would again. In fact if done correctly, when you use such a format, it can be rules neutral. It can work with any game or edition so long as the instructions, steps and details are well thought out or detailed enough. It would be the difference between buying a Faerun or Eberron campaign setting book and buying a Build Your Own setting book. A difference which would be infinitely more useful in my game, as I am not running Faerun or Eberron.
I think it is a better idea, I also doubt WotC can do it. I do not think they have the skill, expertise or desire to do it but it would be MY preferred setting book.