Obesity
The CDC announced that poor diet and physical inactivity (16%) are closing in on tobacco (18%) as the leading actual cause of death in the US. In 2000, poor diet and physical inactivity were the cause of 400,000 deaths--now compare that to the 9/11 death toll of 3,000.
The physical inactivity has a lot to do with our standard of living (cars, elevators, etc.) and the design of our cities (too far to walk to stores, no sidewalks, etc.)--not to mention laziness. But what about poor diet? I feel that our government is partly responsible for our poor diets. A lot of agricultural subsidies have made food (especially unhealthy food) too cheap. The biggest culprit? Corn, the most heavily subsidized crop in America. Cheap corn is used to make cheap corn sweetner for all those Super Sized soft drinks and Big Gulps. Cheap corn is also used to feed cattle and give us cheaper hamburgers.
The government has mentioned a few ideas of how to tackle the obesity problem, but they're not considering stopping the subsidies that help make us fat. Unfortunately the agricultural lobby is too strong and no politician will ever touch agricultural subsidies.