I'm of the mindset of staying in the middle and not going to either extreme.

My two vehicles, X5-M and Outback XT, are not the most fuel efficient but neither are they the least fuel efficient. They are the vehicles I like to drive and so I drive them. I'm not going to buy a more environmentally friendly vehicle just to be more environmentally friendly (though earlier in the year I had considered the purchase of a Chevy Volt).

Having said that I do attempt to keep my environmental impact low. I maintain the vehicles to ensure emissions are in check. I recycle things where possible (I take my trash out once every six months, recycle ever other week). I try to minimize waste where possible by reselling things or giving them away (free section of CL is great for this).

IMO it's all about balance.