Bad idea of the week
OK, it's not really new. But - Earthships.
Earthships are 100% sustainable homes that are both cheap to build and awesome to live in. They offer amenities like no other sustainable building style you have come across. For the reasons that follow, I believe Earthships can actually change the world.
Honestly, if you want one of these to live in like a hobbit out in the country, that's your prerogative. But this kind of fantasy-house of green design (some of which is not really useful) has no place in cities. It perfectly illustrates the "gizmo green" mentality that dominates too much of the effort in the world of sustainable design. It's been said many times before, but the single best thing anyone can do to be more "green" is live somewhere that you don't need a car. Walkable communities are far greener than any Xanadu-inspired green home.
Have a look, and especially read the comments if you think I'm overly negative.