"Barrick may be getting off the hook but this technical default creates a shortage of physical gold."

Why?

Can't they just pay the difference as you or me would if we were speculators in the futures market and had no gold to deliver?

http://www.investopedia.com/university/futures/futures2.asp

Profit And Loss - Cash Settlement
The profits and losses of a futures contract depend on the daily movements of the market for that contract and are calculated on a daily basis. For example, say the futures contracts for wheat increases to $5 per bushel the day after the above farmer and bread maker enter into their futures contract of $4 per bushel. The farmer, as the holder of the short position, has lost $1 per bushel because the selling price just increased from the future price at which he is obliged to sell his wheat. The bread maker, as the long position, has profited by $1 per bushel because the price he is obliged to pay is less than what the rest of the market is obliged to pay in the future for wheat.

On the day the change occurs, the farmer's account is debited $5,000 ($1 per bushel X 5,000 bushels) and the bread maker's account is credited by $5,000 ($1 per bushel X 5,000 bushels). As the market moves every day, these kinds of adjustments are made accordingly. Unlike the stock market, futures positions are settled on a daily basis, which means that gains and losses from a day's trading are deducted or credited to a person's account each day. In the stock market, the capital gains or losses from movements in price aren't realized until the investor decides to sell the stock or cover his or her short position.

As the accounts of the parties in futures contracts are adjusted every day, most transactions in the futures market are settled in cash, and the actual physical commodity is bought or sold in the cash market. Prices in the cash and futures market tend to move parallel to one another, and when a futures contract expires, the prices merge into one price. So on the date either party decides to close out their futures position, the contract will be settled. If the contract was settled at $5 per bushel, the farmer would lose $5,000 on the futures contract and the bread maker would have made $5,000 on the contract.



But after the settlement of the futures contract, the bread maker still needs wheat to make bread, so he will in actuality buy his wheat in the cash market (or from a wheat pool) for $5 per bushel (a total of $25,000) because that's the price of wheat in the cash market when he closes out his contract. However, technically, the bread maker's futures profits of $5,000 go towards his purchase, which means he still pays his locked-in price of $4 per bushel ($25,000 - $5,000 = $20,000). The farmer, after also closing out the contract, can sell his wheat on the cash market at $5 per bushel but because of his losses from the futures contract with the bread maker, the farmer still actually receives only $4 per bushel. In other words, the farmer's loss in the futures contract is offset by the higher selling price in the cash market - this is referred to as hedging.

Now that you see that a futures contract is really more like a financial position, you can also see that the two parties in the wheat futures contract discussed above could be two speculators rather than a farmer and a bread maker. In such a case, the short speculator would simply have lost $5,000 while the long speculator would have gained that amount. In other words, neither would have to go to the cash market to buy or sell the commodity after the contract expires.)