Just an aside (not to derail this thread onto the issue of villas and environmental sustainability),

here's a little more on Al Gore's new $8 million villa:
Gores Buy Montecito Villa

and maybe the rest of the story?
Ecorazzi.com on how the Gores equipped their Tennessee home

Most of the cost of this estate is no doubt the property itself (high-cost real estate with ocean view), not the house itself or the pools, etc.   As to how big a carbon footprint such an estate leaves, that depends a lot on how much of the home (and pools, etc.) is being used at any one time, what kinds of energy sources and conservation devices they use, what kinds of landscaping methods they use, etc.   And it sounds like they bought an existing house, so the 9 bathrooms may not have been their idea. However, if you are entertaining guests in a large house, having bathrooms on all floors and adjacent to the various rooms (5 bedrooms, a dining room, a rec room or exercise room) and next to the pool doesn't seem unreasonable. Bathrooms aren't using energy or water when they're not in use.   
The issue of environmental stewardship has more to do with how you use and maintain your property than with how much you own.