I recently listened to a great radio broadcast about the farm bill and a big part of the discussion was about food stamps. One panelist made a good point which is that we ought to call food stamps what they are which is essentially income. True, they can only purchase food but for most of their recipients, the food they purchase would likely have been purchased none the less and the opportunity cost of the food stamps is whatever they purchase with the revenue they would have allocated towards food. -This isn't to say that assistance isn't needed but we ought not think of food stamps as only providing food. -It's indirect income.
The recipients might allocate the money they would have used on food to purchase medical supplies or to make an auto payment and therefore have the ability to drive to work. Or, they could use the savings to purchase cigarettes and mountain dew. My guess is that both happen.
Tangentially, they cited a study that showed that the diet of the poor in the US is not worse than that of the middle class. -I found this hard to believe.
[edit] during the broadcast a woman from Michigan called in and said she had been on food stamps for several years. Her husband is self employed and they are trying to start their own business. They have to re-apply and show financial justification quarterly for the "stamps". She wishes more than anything that they could get off the program but his business isn't doing that well. So, for them the program hasn't discouraged work at all. They are working hard and their goal is to not need the assistance eventually. These scenarios exist and I'd be willing to bet they exist more often than not.