Clunker Scams: Got One That Works?

Seems like every fool on Craiglist is pushing a "cash for clunkers" scam. The owner of this true clunker Pontiac in Pennsylvania is offering up his junk to help you win a $4,500 new car voucher. Cost is $700. Then you've got buyers like this guy looking to purchase a clunker cheap before they hit the showroom. Problem is, we're pretty sure that scam doesn't work. But we're also sure that with $3 billion in the "cash for clunker" budget, someone has figured out a nice scam. Any ideas?
The buy a clunker to trade move is against the rules, which say you have to have owned the clunker for at least a year. Same for the "I'll use my car and split the rebate with you" scam. Unless the guy who owns the junker buys the new car and immediately sells it to the new owner, I don't see how that one could work.
So we're guessing that when the scams come to light, most won't be on the consumer end, though some savvy buyers will have figured out some way to work the program. We'd look instead at scrap yards and car dealers, historically run by two of the most honest groups of folks out there.