One key reason not to leave the eurozone is that it will destroy your domestic banking system. But if depositors start to think your country may leave the eurozone then they'll start withdrawing money from your banks en masse and your domestic banking system will be destroyed anyway. So if your domestic banks are doomed, it's actually better to get ahead of the curve so you can leave and start imposing capital controls ASAP.
This, incidentally, is why any "firewall" strategy is going to be hard to implement. If you're Portugese and Greece leaves the euro, isn't your next move going to be to close out your local bank account to either hold cash euros or shift the funds into a German bank?
TODAY IN SLATE
The Irritating Confidante
John Dickerson on Ben Bradlee’s fascinating relationship with John F. Kennedy.
My Father Invented Social Networking at a Girls’ Reform School in the 1930s
Renée Zellweger’s New Face Is Too Real
Sleater-Kinney Was Once America’s Best Rock Band
Can it be again?
The All The President’s Men Scene That Captured Ben Bradlee
Is It Better to Be a Hero Like Batman?
Or an altruist like Bruce Wayne?
Driving in Circles
The autonomous Google car may never actually happen.