Who Runs The Commodity Markets?

Reuters, via nc links:

For the small club of companies who trade the food, fuels and metals that keep the world running, the last decade has been sensational. Driven by the rise of Brazil, China, India and other fast-growing economies, the global commodities boom has turbocharged profits at the world's biggest trading houses. They form an exclusive group, whose loosely regulated members are often based in such tax havens as Switzerland. Together, they are worth over a trillion dollars in annual revenue and control more than half the world's freely traded commodities. The top five piled up $629 billion in revenues last year, just below the global top five financial companies and more than the combined sales of leading players in tech or telecoms. Many amass speculative positions worth billions in raw goods, or hoard commodities in warehouses and super-tankers during periods of tight supply.
U.S. and European regulators are cracking down on big banks and hedge funds that speculate in raw goods, but trading firms remain largely untouched. Many are unlisted or family run, and because they trade physical goods are largely impervious to financial regulators. Outside the commodities business, many of these quiet giants who broker the world's basic goods are little known.

The article profiles, among others, Cargill, Koch Industries and ADM.  At a certain point, you have to wonder, when is enough enough for these folks?  They get control of a larger and larger percentage of the market in a commodity, and then squeeze.  Will there ever be a time when they don't want even more?