I've had this thought too regarding precious metals: along with the useful elements of silver that he described is also the fact that it's probably a lot more useful for any kind of barter. In tough times there probably won't be an easy way to make change for an ounce of gold for example (like trading for some meat or other supplies), so trading an ounce of silver for something useful could be quite valuable. If you only had gold and wanted something relatively small and the other person didn't have any way to give you the small thing and something of equal value for the rest of the gold, then it could be quite a loss to trade the gold. Having many ounces of silver instead of one ounce of gold, while less convenient to carry, could be much more practical for barter situations.
Then again, you can't eat precious metals.