When the Chicago Merc raised silver margins four times in the past week, for an increase of almost 85%, it took aim at the most capital-sensitive layer of the cake -- the day traders and small retail investors. In addition, silver ETFs such as the Powershares DB Silver ( DBS), which use futures, were forced into liquidating as well. A market that has moved parabolically as silver had in the past several months was particularly vulnerable to a selloff, and all that was required was a tipping point -- which these margin increases provided. Going back to our cake, much of the top layer in silver has been sliced away -- and that 25% selloff indicates just how thick that layer of money was. And what about oil? If margin increases could be a tipping lever for a big selloff in silver, could we do the same to crude oil and slice the costs that people are paying at the pumps? Increasing margins would be an excellent start, and one of the arguments that the CFTC is waging among itself as part of its rule writing mandates from the Dodd-Frank bill. But that big top layer of retail speculation fueling silver is a relatively much smaller layer in oil's "cake," and slicing the thicker layers of investment interest in crude will require a much bigger knife. An enormous amount of capital, perhaps as much as $300 billion, is engaged in energy through index investment, the speculative proxy of institutional and private-wealth investors. Getting at that layer of speculation will require restricted access to the commodity markets from these instruments, owned and run by powerhouse funds like Pimco, Oppenheimer, BlackRock and Goldman Sachs. Being able to remove that capital from the oil market might drop the price that consumers pay for gas as much as a dollar a gallon as quickly as money has fled from silver. It would, however, require a more concerted effort from Congress and the SEC, as well as from exchanges. Still, the silver move provides the lesson of just how much speculative money has been fueling price gains in all commodities in the past year -- and just how quickly prices can come down if some available tools are used to chase some of that money out.