Two opinion pieces appearing in the Times over the past 3 days give some insight into a few of the ways that politicization of farming is effecting what foods consumers have access to and how much they are paying for it.
In the first we have a small farmer (100 acres) who needs more land, rents out 25 acres on nearby farms, plants tomatoes & watermelons, and finds out that his landlords are being punished (fines and loss of future subsidies) by the Farm Service because those crops were planted on land covered under the corn subsidy.
In the second, there's the skyrocketing price of wheat as a result of the incentives (that same subsidy) to produce corn - the crop of which 14% of this countries output in 2006 went to producing biofuels like ethanol. The same ethanol potentially takes as much or more energy (in the form of petroleum products for equipment and fertilizer for massive corn fields) to produce than it provides in return.
I don't know diddly about macroeconomics and I haven't picked up the farm bill (although it might be interesting reading), but I can see some of what is coming out of this giant, twisting machine: the big vegetable farmers (don't want small vegetable farmers), the big corn growers (love the subsidies) and the government (loves ethanol because it's not oil) are making out alright. Small, non-commodity crop farmers aren't. And we, the ones looking for good, local, fresh food have less of it to choose from.