Courtesy of a Google+ friend, I stumbled across this graph, originally from The Atlantic:
What this graph demonstrates is quite simple. Take any random collection of nations. Former member states of the Soviet Union. All the countries along the 5th parallel. Members of a reconstituted Ottoman Empire. Or even countries beginning with the letter “M”. In all cases, the countries you pick turn out to be socioeconomically less diverse (i.e., they have more in common) than the major member states of the European Monetary Union.
I don’t know if it really makes the Eurozone doomed, but it certainly shows that holding it together will be quite a challenge.