Further, it's worth pointing out that Krugman endorses a monetary system that makes people poor, via inflating the money supply by printing funds to underwrite policies that benefit, primarily, politicians.
A currency whose supply is fixed, or whose inflation rate is constant and predictable (like bitcoin) is better for facilitating transactions.
When you have a variable (and often high these days- in the US money supply is up over %50 in recent years) rate of inflation, it wrecks havoc with prices and other signals causing malinvestment and worsening the economy.
Something that Krugman, to my knowledge, has never answered for.
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Since I am not allowed to reply to the person below me:
It's quite silly to to say that a limited supply of a currency is bad for it. There is little incentive to hang onto bitcoins. A simple example will prove this to you: The amount of computer you can get for a given amount of money improves dramatically every three years. You could just hold onto your money and buy a much better computer. Thus, relative to computers, the dollar is deflationary.... yet people still buy computers.
This is the kind of argument Krugman gives because he wants to excuse the inflation that has destroyed the dollar, and the economy.... but it is nonsensical. People still buy computers.