But anyway - I'm pretty sure Europe has a second set of currency designs as a contingency plan for such a situation. So if Greece actually started to massivley attack the Euro with counterfeit bank notes, expect a hastily organized exchange against another set of notes.

Given the incredible hassle that produces that would, of course, eradicate whatever goodwill Greece has left with the other European countries and their citizens.

And it might even give a political opening for a fracturing into a northern hard and a southern weak Euro. Feel free to imagine the consequences.