Is Cash for Clunkers an environmental coup or just another Detroit bailout?

Starting today, the government's Car Allowance Rebate System (CARS), aka "Cash for Clunkers," will go into effect. The controversial program, which has drawn both the appreciation and the ire of the environmental community, is designed to stimulate the automobile industry and encourage the adoption of more fuel-efficient vehicles. The program is currently limited to 1 million car vouchers, and will run until November 1, at which time Congress will decide whether or not to keep it.

CARS defines "clunkers" as driveable vehicles that are 25 years old or younger, get fewer than 18 miles per gallon, and have been insured by the same person for at least one year; here is a list of cars that qualify. If owners trade eligible cars in for more efficient models, they receive cash rebates that are scaled, based on the improvement in mileage. Trades that improve mileage by four miles per gallon qualify for $3,500, while trades that get 10 miles per gallon better mileage qualify for $4,500.