(By Ken Thomas, Associated Press) The Cash for Clunkers program encouraged more than a half-million Americans to dump their gas guzzlers for new cars and provided a much-needed, short-term boost to the economy.Critics of the program, which expires Monday, say that's hardly the whole story. They view the $3 billion program as a lemon of a policy, an example of the Obama administration'a willingness to cherry-pick an industry to help and stick taxpayers with the tab.Though the merits and flaws will be debated for years, the early assessment has to start with the program's overwhelming popularity.Car buyers can still take advantage of the $3,500 or $4,500 incentives this weekend; the program ends Monday.