Cash for clunkers is a program only a politician could love. The idea that replacing a working car with a new one that gets better gas mileage is somehow good for the environment is daft. Carbon emissions aren't the end all and be all of good environmental stewardship. Recycling and reusing what we already have is always better than needlessly upgrading to something greener.
Lets put it this way... You wouldn't take your 2 year old Plasma to the dump just because you can get a new LED TV that draws half the power. Or if you would you're an idiot and don't deserve money from the government.
Here's a short list of awesome cars that the government thinks are such an environmental menace they must be destroyed asap. ~via Jalopnik 1987 Nissan 300ZX 2x2
1990 BMW 525i
1991 Alfa Romeo 164
1993 Acura Legend
1987 Oldsmobile Cutlass Supreme
1996 Mitsubishi 3000 GT Spyder
2004 Mazda RX-8
1991 BMW M3
I'm sure all those 1991 BMW M3 owners are just so excited for this program. Finally a dealer will give them $4,000 trade in on a car worth almost $15,000.