The securities fraud case against Goldman Sachs in the United States involving certain mortgage bonds has once again cast a spotlight on financial derivatives.

Critics charge that these products of synthetic collateralized debt obligation (CDO) serve no real purpose in the financial markets. Trading in derivatives is similar to rolling the dice, some say.

Others contend that synthetic CDO was just a kind of financial derivative that could help facilitate the flow of capital by allowing a wider spread of risks among mortgage lenders, investors and speculators.