So it goes without saying that ECB President Mario Draghi is powerful.  He decides how much money is printed in Europe and what the cost of borrowing that money will be.  But dig deeper and you'll find that the ECB exerts far more control over events in Europe than the Fed does in the US.

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More obscure than the bond-buying program but far more powerful is the little-known "risk control framework".  Normally, the ECB is willing to provide loans to banks as long as they can pledge assets that are listed on its "eligible collateral list".   However, the risk control framework allows the ECB to deny credit to any bank or reject any assets as collateral should it see fit.  Specifically:

the Eurosystem may suspend or exclude counterparties' access to monetary policy instruments on the grounds of prudence

and

the Eurosystem may also reject assets, limit the use of assets or apply supplementary haircuts to assets submitted as collateral in Eurosystem credit operations by specific counterparties.

The ECB has used the risk-control framework to control events at a number of key junctures in the euro crisis.

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All told, the story of ECB's serial use of its risk control framework raises pretty serious questions about whether it is has been a good idea for Europe to provide this much power to a single unaccountable institution.