The difference between today and before is that old money is rarely parked in a single business model. The sophistication in finance, and the spread of public companies means the Waltons don't only stay rich as long as Walmart is successful. In fact, I'd bet their wealth is affected far less by Walmart than it is by the tens or hundreds of hedge funds and VC firms they are invested in.

Money is rarely parked at any one place today, but rather, is largely distributed throughout the economy.