Another thing that has driven up corporate profits and stock prices is also unsustainable - outsourcing the US economy. The US economy became the power house that it did during the 50s and 60s. The reason that occurred was a strong middle class which translated to customers with disposable income. Yes, the consumer has been spending but not with earned income but through debt which can't be sustained. The inevitable consequence will be a big crash - maybe this is it maybe not but it will come. All Ponzi Schemes eventually come crashing down.
Also see Smoke and Mirrors. This is the important part:
As Murray Rothbard explains, in The Austrian Theory of the Trade Cycle, America’s debt-driven "prosperity" is a mirage built upon the opiate of easy credit. Alan Greenspan’s multiple interest rate cuts, as Dr. Rothbard conveys, is nothing new in the field of central banking:… the point is that the credit expansion is not one-shot; it proceeds on and on, never giving consumers the chance to reestablish their preferred proportions of consumption and saving, never allowing the rise in costs in the capital goods industries to catch up to the inflationary rise in prices. Like the repeated doping of a horse, the boom is kept on its way and ahead of its inevitable comeuppance, by repeated doses of the stimulant of bank credit.