Like a house of cards, currency unions look stable until some tiny structural flaw gives way. The eurozone's Achilles heel was always the lack of a unified treasury that could levy taxes and issue debt without regard for any national parliaments. Did you get that Greek reference? Achilles heel, eh? If you didn't, you owe me a gyro. You'll be paying for those in Greek drachmas again soon enough.
Full disclosure: No positions in European currencies or bonds at this time.