Conventional wisdom has it that you should devote a small portion of your portfolio to gold, which should maintain its value or appreciate in times of turmoil for financial markets.

But that relationship has broken down recently. While markets have been roiled by debt crises in Greece and Puerto Rico and by a plunge in Chinese stocks, the precious metal has dropped to a five-year low, trading at $1,085.40 an ounce late Tuesday.

This has Mohamed El-Erian, chief economic adviser at Allianz, questioning gold's purpose. "The most consequential hypothesis of all is that gold may be losing its traditional role in a diversified investment portfolio," he writes in the Financial Times.

It's structural rather than cyclical forces holding gold down, El-Erian suggests.

For example, "gold has become a lot less attractive to investors as a result of the lack of meaningful inflationary pressures," he maintains. U.S. consumer prices rose just 0.1 percent in the 12 months through June.

But not everyone is bearish on the precious metal. Some investors see its current weakness creating the best buying opportunity since the 1970s, when gold surged from $100 an ounce to more than $920, says Albert Edwards, head strategist at Societe Generale.

“Western central banks have set us up for an even bigger version of the 2008 great financial crisis/recession,” he writes in a July 30 report obtained by Newsmax Finance.

“This time, rock-bottom interest rates and large fiscal deficits will mean only one thing: QE [quantitative easing] will be stepped up to such a pace that you will hear the roar of the printing presses from Mars. Gold is a must-have holding in that world.”

Central banks around the world have used quantitative easing—mostly bond purchases—to keep interest rates down and stimulate their economies. The Federal Reserve finished its QE last year, but the European Central Bank and the Bank of Japan still have large QE programs in place.

The recent drop of commodity prices to 13-year lows will keep the pressure on central banks to ease, Edwards says.

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