Just a couple comments:
One, those of you commenting on "Why do people need to buy these big 4x4's " clearly don't understand the concept of personal choice. I choose to drive a Tahoe for the same reason I choose to eat Red Meat and drink the occasional pint, because I can. If you feel the world needs everyone driving a Segway around, run for office.
Two, those of you mocking the Tahoe as "green car of the year" need to remember something if you don't actually live here in the states: You can't buy diesels here.
No, seriously...this isn't a joke...you can count the number of diesel cars on like one hand. If you came over here and chose 1000 random people, none of them would own a diesel. So...for us...40-50mpg is unheard of....15mpg is good for a big V8 in a big Truck and 25 or so is amazingly good for the highway. To take a giant American warhorse Tahoe and put a hybrid in it and have it get 25mpg is a big, big, big deal here. Next it'll be the Corvette..and then...all we'll have are Hybrids. Its conditioning the public to get ready for Hybridization.
If you don't live here in the States, you wont "get it" because you're used to seeing microscopic cars with 1.4l diesel engines that get 40mpg, and everyone you know owns one....here....you couldn't find a diesel car if you looked hard for hours.