There's another societal trend at play here, and that's the increasing pace of technological change and market disruption. Increasingly, "income stocks" are becoming "death stocks" - rather than companies with stable income streams for the foreseeable future, they are companies whose products and business models have become obsolete and who are just awaiting a competitor to replace them.

The days where the economy was relatively stable and large companies had wide moats against competition are largely over. The last 15 years has seen a large number of huge household names go bankrupt entirely, from Kmart to Sears to Toys'r'us to Chrysler to GM to MCI/Worldcom to Bear Stearns to Lehman Brothers to Wachovia to virtually every airline. Many more are now at risk, from Visa & Mastercard to Walmart to every hotel chain.

All of these huge returns for private tech companies are coming at the expense of their competitors, which are largely the big public companies that many people have their retirement money invested in.