@High Seas,
I agree with you concerning the evident volatility of markets and the potential for inadvertant fast-developing unstable consequences in the dynamic at work in today's markets.
My point with Cicerone (and Thomas and Cyclo) regards their (remarkable to me) and (in my view) naively uncritical assumptions that the domain of beneficial application of some not-very-original ideas attributed to Keynes, relating to deficit based government stimulus during cyclic economic contractions, has no boundaries at all. In fact government deficit spending has inescapable negative consequences, including future interest and principal payments and effects on the future credit worthiness of the borrowing government. If the cumulative debt relative to GDP (and potential tax farming source) is low, these consequences are minor and not determinative. However if such debt levels are very high the negative effects can dominate, and even create a different dynamic entirely. (This latter issue relates to your expressed concerns regarding instabilkity and power law effects in todays world financial markets).
Clearly Greece, with a public debt of 140% of GDP, soaring bond yields, and a currency it can't depreciate, has no Keynesian option for the restoration of its economic growth. (I believe there are other negative factors at work in Greece as well, mostly involving a long-standing corruption of public attitudes concerning work and economic rewards.)
It can be argued that the inability of Greece to depreciate the Euro or default on its Europeran lenders alone prevents the Keynesian option. I don't agree in that default isn't an option for the United States either.
The question for us is with a Federal debt around 65% of GDP (and rising very fast) and a cumulative State & local government debt adding another 30%, does the United States have any Keynesian option either? Very clearly the weasel Krugman, and his acolites, Cicerone, Cyclo and Thomas believe do indeed have such an option. However I note that none of them has ever suggested something like that for Greece. Why?
At what point does the dynamic change?
If, for example, we had no debate or struggle over raising the debt ceiling, and, instead, merely sailed along doing a Krugmanesque 3 trillion "stimulus" with borrowed money (presumably taking advantage of a stupid, passive world of lenders in a period of low interest rates) and "protecting" our sacred entitlements ... would the world simply accomodate us? Or would it react, leaving us instead to face lower bond bids (higher interest rates) and exploding commodity prices that could set of an exponential (power law) catastrophe in our balance of payments, thereby debasing our currency and wiping out the capital of our corporations and all savers - and, with that, our ability to ever recover from it ?