Farm subsidies are both the single most important national security policy a nation can have, and an incredibly inexpensive yet extremely effective insurance policy.
The Omnivore's Dilemma points out that the food economy doesn't even behave like the normal economy - supply is variable due to weather (bumper crop vs famine year) but demand is inelastic, people generally eat the same amount year-to-year. How do you grow your food business if people only eat so much? One method is to increase portion sizes.
Farm subsidies are both the single most important national security policy a nation can have, and an incredibly inexpensive yet extremely effective insurance policy.