To a point, I do have to agree with the "too many cooks" concept regarding campaign settings (and to a degree, other games/forms of media). I also think that, to a certain extent, things can be dragged out so much that it kills any enjoyment the original(s) brought to the table.
Forgotten Realms, pre-Time of Troubles, pre-tons-of-tie-in-novels/book-series, IMHO, was a cool setting. I liked the FR of the Grey Box days. However, I lost interest in FR when (a) a lot of books set in the FR were released, often introducing new weird stuff that many players of the game would want to use/emulate, and (b) FR was blown up ala Time of Troubles. That really killed my interest in the setting.
Along the same lines, I grew to dislike Dragonlance because it seemed to, IMHO, basically retread the same old issue over & over again: the epic clash between good & evil, providing a small amount of peace afterward before the whole place goes to the Abyss in a Handbasket once more.
Eberron is nice; it has potential. However, part of me thinks is that all it will take is a fair amount of time for it to wind up getting a dramatic change. Will it go through another war just as 4th ed. D&D shows up (whenever it does)? Will some books in the series introduce some weird, new stuff that'll mess up the feel of the game, sorta how the FR was post-ToT? I dunno. But then again, I could see it happening. It could happen as soon as there's a creative team change, or it could happen as soon as the setting gets a real sales slump. Ya never know.
But, it's pretty much my dissatisfaction with the way a lot of campaign settings evolve (or OTOH, my general uninterest in the settings in the first place) that has led me to pretty much sticking with homebrew stuff for my own campaigns. In a way, sorta how Greyhawk originally was--a locale with little originally defined that could easily have stuff dropped in if need be--it pretty much became defined more & more as the players went along.
