It probably would've been harmless from an anonymous poster on a D&D message board or even in behind closed doors at the designer meetings. But the people in control of D&D have, I think, a responsibility to acknowledge that what they don't use -- indeed, what a majority of players don't use -- someone, somewhere, probably does.
They should figure out why and how those people use what they do, and what they like about it, and what they don't.
Because, lets face it, D&D players in general do something that they regard as lots of fun that the majority of people don't. Sitting in a room for 4 hours on a sunny weekend afternoon with 4-5 other adults and pretending to be magical gumdrop elves is not any nation's national passtime, and it never will be. D&D designers understand pretty well what makes that fun. They should be able to understand what makes The Plane of Vacuum fun, too. And once they understand that, they can highlight that, expand it, make it better, draw it larger, and get more people interested in it.
They also shouldn't be astonished at people taking hyperbole seriously. If I were to say "4E IS A VIDEOGAME!," you could watch and see the offended people coming out of the woodwork, as if that phrase magically brought them into existence. And I'm just some dude on a semi-obscure D&D message board. I have no power, and no one should care what I think.
I don't exactly blame them for not wasting space detailing the quasi-elemental plane of vacuum, or the guardinals, or Bytopia. It's certainly not a priority. It is, however, important for you, if you are in charge of D&D, to know how and why D&D players have enjoyed these things in the past, so that you can continue to help them enjoy them going forward, and maybe even bring them to a bigger audience.
