This is a systemic problem. Any valid explanation of price increases in a commodity, e.g., oil (gas), has to explain why prices are rising almost across the board.
This is almost exactly the point the article is trying to explain: commodity prices are rising across the board in line with the commodities index, but why should there be an index at all? In the market you have the supplier, buyer, and consumer. The "speculator" was placed into the mix with a limited role for providing liquidity; this role was intentional and helpful since in the real world there could be a delay between the time a grower/supplier and buyer/cereal producer actually needed what the other had (raw material or cash); with the speculator there was always the opportunity to buy or sell. However, there were intentional, specific limits placed on the speculator. This was to ensure he couldn't corner the market and artificially skew prices. As long as these limits remained intact the market operated as designed, and the actual price of commodities reflected real world supply and demand (since the main players in the market were physical hedgers - people who actually had stake in/cared about the physical commodity). Goldman Sachs was able to get these "speculator handcuffs" removed. This means the actual market price for commodities doesn't necessarily reflect supply and demand. Rather, it also has the component of speculation priced into it. We can see this even within these last few days. The price of a barrel of oil was skyrocketing above $100; this seemed to make sense due to the unrest in the Middle East, then amazingly with the earthquake in Japan it quickly dropped below $100. In such as short time was there really an escalation then de-escalation in the demand for oil!? Of course not. The price was following speculation, people who are only in the market to make money. The end result is that ordinary consumers must pay at the pump what the whims of investors say, never mind progress made whether politically or technologically, or reductions by consumers in a recession to ease pressure on demand and oil prices. Natural gas is not as attractive to speculators as oil.