Point to ponder: Clunker arbitrage.

Consider this:
Congress Close on "Cash for Clunkers"

So, just how may old cars can I buy from people for less than $4,500 to trade in for a new car? And, are these vouchers stackable? Who thinks I can get a Mercedes in exchange for a dozen Darts, T-1000s, and Pintos?

Consider some other unintended consequences. Are these vouchers transferable? I can easily get $2,000 cash on eBay for a $4,500 voucher.

For the record, here are some good arguments on why not to implement a "cash for clunkers" program:
No Cash For Clunkers