"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?

I think the answer to your question lies in this paragraph:

"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."

If the buyer of the contract actually wants to take delivery, that creates a problem if there is no physical gold available to deliver. Of course, COMEX has re-written the rules allowing shorts to deliver in GLD shares, but this could still be a problem if a deep-pocketed buyer takes exception to such a "delivery".