Have commented on a few blogs that bring up the meme of collateral shortages.
Commodity money: It's back! (and it sucks) at Macromania
Is the Fed our savior in financial regulation? at Marginal Revolution
Why the Global Shortage of Safe Assets Matters at Macro and Other Market Musings
The idea of a scarcity of shortage of safe assets is nonsensical to me.
I just don't think this can be a real issue. If the quantity of "safe assets" somehow collapses, then the prices of remaining "safe assets" will rise to meet the market's demand for safe collateral and stores of value. You can't have shortages in financial markets. Do you think you can?
The idea that there can be a shortage of good collateralizable financial assets sounds fishy to me. Prices for those assets will simply rise until their price is sufficient to meet the demand for good collateral. The same with an excess demand for money - prices will simply fall to meet that demand.