We've known for quite a while that they're a boondoggle. Ethanol freezes in pipes, so it must be transported by truck. It's been estimated that it requires a gallon and a half of gasoline to transport a gallon of ethanol!
But now it seems that corn ethanol is itself more polluting than gasoline is- which raises the obvious question of why we should be producing ethanol in the first place. Well, states which depend on agriculture to a substantial degree have a large economic investment in it, and criticizing it in places like Iowa is not a politically healthy thing to do.