Via Zero Hedge:
It’s a lump of metal with no cash flows and no earnings power. In a very real sense it's not intrinsically worth anything. If you buy it, you're forgoing dividend or interest income and the gradual accumulation over time of intrinsic value since a lump of cold, industrially useless metal can offer none of these things. That forgone accumulation of wealth is like the insurance premium paid for a policy which will pay out in the event of an extreme inflation event.
Is there anything else which will do that? Some argue that equities hedge against inflation because they are a claim on real assets, but most of the great bear market troughs of the 20th century occurred during inflationary periods. A more obvious inflation hedge is inflation linked bonds, but governments can default on these too. More exotic insurance products like sovereign CDSs, inflation caps, long-dated swaptions or upside yield curve volatility all have their intuitive merits. But they all come with counterparty risk. Physical gold doesn’t. Indeed, during the “6000 year gold bubble” no one has defaulted on gold. It is the one insurance policy which will pay out when you really need it to.