This blog contains much discussion of McMansions. It is helpful to start with an accurate definition of such homes. Here are four posts that explain what makes a McMansion:
Defining a McMansion, Trait #1: Size
Defining a McMansion, Trait #2: Relative size
Defining a McMansion, Trait #3: Architecture and design
Defining a McMansion, Trait #4: A symbol
For a more formal discussion of this definition, see “Competing Visions of the Single-Family Home: Defining McMansions in the New York Times and Dallas Morning News, 2000-2009″ published in the Journal of Urban History.