Despite all these measures, which obviously make the QE programme less problematic than earlier sovereign bond purchase programmes which aimed to reduce the risk premia of individual countries, one important risk nonetheless remains: The national central banks will become the most important creditors to their governments, which might ultimately put the independence of monetary policy at risk.
The purchases will make life easier for finance ministers. They will not be amused when the Governing Council considers exiting its ultra-loose monetary policy. And they might be tempted to put political pressure on the Eurosystem.