Would that it were so difficult

I find myself on the one hand strangely agreeing with the Cato Institute...
Consider how easy it would be to game this giveaway program by using that $4,500 voucher to buy a big SUV or V-8 muscle car.

First of all, with Chrysler and GM dealerships folding, it should be easy to buy a mediocre Chevy Cobalt or Dodge Caliber for about $10,000 more than the voucher.

What you do next is sell that boring econobox, even if you end up with $1,000 less than you paid — that still leaves you with $3,500 of free money, courtesy of taxpayers.
...and yet having to say that the Cash for Clunkers program is even worse than they say. Apparently it's as popular as it is in part because it's far easier than that to buy your next future clunker:
The $1 billion was to provide rebates of $3,500 or $4,500 for people who traded in older cars rated 18 miles per gallon or less for new ones rated 22 mpg or more. The old cars are scrapped. [...]

If more money is earmarked for the program, it should require the new cars to get better fuel economy than under the original program, say Sens. Dianne Feinstein, D-Calif., and Susan Collins, R-Maine, who both played a role in creating the program.

"We will insist than any extension of the program requires that the minimum fuel economy improvement for newly purchased vehicles be at least 2 miles per gallon higher than it is under the enacted Clunkers program. It is also important to include lower-income consumers who are disadvantaged under the current program. So, we would also include a voucher for the purchase of fuel-efficient used vehicles," they said in a joint statement late Thursday. "We believe that any extension of the 'Cash for Clunkers' program must go further in advancing the goals of better fuel efficiency and greater emissions reductions. We will not support any bill that does not meet these goals."
It appears you get the money as long as you trade in the low mileage vehicle, and there was never a stipulation in the bill that you have to buy a higher mileage vehicle. Stupid. Stupid. Stupid. Hereby, I hand it to the wingnuts. It's your day.