Perhaps the following parable is not entirely fair to the euro, but nevertheless the parallels seem striking.
Consider a young couple contemplating marriage, but who are unsure whether to take the big step. Instead they decide to test things out by opening a joint bank account. At first things go remarkably smoothly. Heady with success, they get the inspiration of extending the financial arrangement to her brother and his sister. Not only do they hope to show their siblings how well they can co-operate, but with four people, the total size of the account reaches the critical threshold needed to receive the exorbitant privileges normally accorded to the bank’s larger customers.
Thanks to a cleverly designed constraint to limit imbalances between each sibling’s deposits and withdrawals, the innovative experiment continues to flourish. There is no real enforcement mechanism, but the two sets of siblings are determined to make the arrangement succeed. Forced to interact routinely, the couple and their siblings start becoming closer. They even start having dinners together on a routine basis.