CGF has long opposed oversized residences in rural areas that dominate the visual landscape, suck up resources, and encourage land speculation. I've never been satisfied with the term "monster home" because the word "home" connotes something positive and cozy, which these buildings aren't. Last fall I thought of and began using the term "monster mansion," a more specific and descriptive term.
In today's SF Chronicle, in a teaser to a real estate column:
"Ditch the monster mansion. If designed right, tiny spaces can make perfect homes."
As far as I can tell from Google, we first used the term this way (it's been used for haunted houses). Life's little victories!
Update: The Chron apparently rotates different teasers, so you might not see the one printed above if you click on the link.