I just finished reading @37Signals product design/development manifesto, "Getting Real." I came out on the other side of this read so full of energy -- motivated to go back to work in the morning, fire everyone except my favorite developer and product person (I'd do the design, natch) and set out to change the world with a kick-ass product. The no specs, get-it-out-in-the-wild and iterate, evolve and grow into something huge approach was the breath of fresh air I didn't know I was missing. But then I stopped and paused to reflect on my current (and frankly, the bulk of my career) situation and reconsidered.
Can an organization that is carrying a full complement of employees, roadmaps, operating plans and budgets adopt this lean philosophy wholesale? I don't think so. There are elements of the approach that can be watered down and used to augment some current behaviors but the kind of cultural shift required by this approach means retro-fitting an existing organization (of a certain size) is not possible.
Here are just three of the areas where I think the "Getting Real" philosophy breaks down with an existing organization:

User experience designer, dad, husband and musician.