Here's an interesting article discussing the environmental damage a Toyota Prius causes Vs a Hummer. Lots of pollution to mine the nickel for the batteries, which make an around the world journey for processing. The energy needed to make a Prius is 50% greater than a Hummer that will last 3 times longer. In addition, I have wondered what environmental damage there will be when all those batteries need to be replaced.
On the lighter side CheatNeutral allows you to offset your extramarital indulgences, much like Al Gore is offsetting his wasteful energy usage with carbon indulgences :)