McMansions

What Atrios said. I wouldn't mind a slightly larger house for when I have company and the like, but my house is in the neighborhood of 1200 square feet. Other than renting out rooms or entire floors of your house I really can't imagine what you can do with 4000 sq ft...and really, excepting very large families, even 2400 sq ft more than covers what a family would have much practical use for.