This is not just about money, but lives. This article in Foreign Policy explains how Wall Street speculation is driving up cost of food and killing people:

The result of Wall Street’s venture into grain and feed and livestock has been a shock to the global food production and delivery system. Not only does the world’s food supply have to contend with constricted supply and increased demand for real grain, but investment bankers have engineered an artificial upward pull on the price of grain

futures. The result: Imaginary wheat dominates the price of real wheat, as speculators (traditionally one-fifth of the market) now outnumber bona-fide hedgers four-to-one.

Today, bankers and traders sit at the top of the food chain — the carnivores of the system, devouring everyone and everything below. Near the bottom toils the farmer. For him, the rising price of grain should have been a windfall, but speculation has also created spikes in everything the farmer must buy to grow his grain — from seed to fertilizer to diesel fuel. At the very bottom lies the consumer. The average American, who spends roughly 8 to 12 percent of her weekly paycheck on food, did not immediately feel the crunch of rising costs. But for the roughly 2-billion people across the world who spend more than 50 percent of their income on food, the effects have been staggering: 250 million people joined the ranks of the hungry in 2008, bringing the total of the world’s “food insecure” to a peak of 1 billion — a number never seen before.