Depends on if it is possible to lose that money in the mean time. If there are lots of robbers in your neighborhood, it might make sense not to have a lot of cash under your mattress.

Okay, but that's not what he said:

>An investment with risk so low to survive two millennia can safely yield 0%.

If risk-free assets garnered 0% interest rates, then the U.S. Treasury would not have to pay a real rate of return on its debt.