The President of the Bundesbank, Jan Weidmann, is against bond purchases by the ECB to keep the rates of the PIIGs stable. He believes that debt monetization is addictive, like a drug.
The endgame of a bond buying program is problematic for the ECB, because of the debt preference it has given itself for its other sovereign bond purchases:
Weidmann also points out another problem with a monetization program that is rarely spoken of. The ECB is not a democratic institution accountable to the people of Europe. Debt monetization mutualizes the risks and costs of all the governments that use the euro, and that action requires the consent of the voters in a democratic society.