The time frame is unclear, but eventually nanotechnology will allow exact copies of more or less anything. This will make cash, gold and many other current measures of wealth nearly worthless.

You're more right than you know. It makes the very *concept* of wealth nearly worthless. If nearly anyone can turn nearly anything into nearly anything else, then they have all the "wealth" they need! Pervasive nanotech could enable a "Star Trek" style economy.

Somehow, institutions will need to be established to keep track of everyone's net worth. What happens when crackers manage successful attacks on these? Shudder.

Why shudder? As long as I have technology to turn garbage into useful stuff at virtually no cost, what should I care what the system says my wealth is? If (when?) nanotech advances to the level where you can copy anything, traditional definitions of wealth will be as meaningless as medieval peerage systems are today.

nanotech might make coined & printed money obsolete, but I disagree about gold & other "precious" metals. There is a world of difference in the energy requirements to do chemical transformation and nuclear ones. So yes, a dollar bill can be duplicated by rearranging atoms of carbon, hydrogen, nitrogen, phosphorous and oxygen....but to make gold you're going to need gold atoms, which is to say, gold.