In fact, we should enforce a 25% MMR rule for these items:
1) Stock index futures for certain financial companies.
2) Certain foodstuffs like wheat, corn, rice, sugar cane, sugar beets, oats, soybeans, millet, oranges, cacao beans, tea and coffee beans.
3) Crude oil regardless of source.
4) Certain industrial metals like aluminum, iron, copper, nickel, tin and titanium.
5) Precious metals (gold, silver, platinum and palladium).
These changes would drive out the "make a fast buck" speculators and results in far more stable pricing, with much less risk of sudden inflationary or deflationary spikes and dips.
How does the short term purchase of a futures contract cause inflation? If the buyer does not take delivery and hide the commodity, he has to sell the contract before expiration.