What if it's Marxian--in the sense that people aren't hoarding liquidity, but that they simply don't, after years of stagnating incomes, have the wherewithal to spend (and it will take many years to rebuild their own asset bases)?
What if it's Easternlinian--in the sense that people aren't hoarding liquidity for safety, but because they know that yesterday's toxic, self-destructive junk just doesn't make them happy?
And what if it's [hmm, I'll need to find a reference for this perspective], in the sense that banks and corporations, no matter how much we pump into their coffers, instead of jumping up and employing people here, paying taxes, etc, will simply "arbitrage" regulation, and offshore, tax-haven, and otherwise simply shift it elsewhere?
In the former case, DeLong, Krugman, and the neo-Keynesian kru are exactly right. Stimulate, reboot, prosper.
But in the latter case, we're lost at sea. No matter how much we stimulate, without fundamental, transformative institutional change, there will be no simple, easy return to prosperity.
Argue with me if you like, but I'd suggest--this Great Stagnation is a combination of all the causes above. Stimulation might get us part way to prosperity. But it probably won't, in the end, get us there.