Reader R.V. Anuradha points me to this Reuters report on the forthcoming U.S. Trade Policy Review done by the WTO:
In agriculture, some programs may provide incentives that are inconsistent with market signals and affect trade when supported output reaches world markets, it said. “The expiration of the 2002 Farm Act, and the current environment of high commodity prices, offers a favorable juncture to introduce policy change aimed at further improving the market orientation of the agriculture sector to the benefit of both consumers and taxpayers,” the WTO said.
From everything I've read about it, it seems like the new Farm Bill was a missed oppotunity in this regard.