Newsweek: High food prices always hit the poor hardest, and these days there is plenty of bad news. Corn prices are nearly $4 a bushel, almost double their 2005 level. In Mexico, for instance, that translates into a 50 percent rise in the price of corn tortillas, which has elicited protests from tens of thousands of workers. Many blame the burgeoning U.S. biofuel industry, centered around corn-based ethanol, for the crunch. Fidel Castro says diverting corn into fuel is a “tragic” turn of …