I’ve heard enough about the “Cash for Clunkers” law to give it a “C-minus.”The only reason it did not fail completely on the report card was because some consumers and companies used it to trade in a real clunker in the name of efficiency.In this economy, who could blame someone for trading in a 1999 Jeep with 150,000 miles on it for the $4,500 rebate.This law gets a C-minus because of what