Economists aren't political scientists, but they aren't stupid. They learn quickly from their mistakes. 

The $150 billion program was economically sufficient, but politically untenable.  Now that this is understood, there is talk is of "restructuring" Greek debt, which is nothing other than to say that the Eurozone will allow Greece to default on part of its debt (to reduce the pain of the austerity measures over the next 10 years). The question is, what comes first: the German elections (next week) or the Greek implosion. It's tough for German Chancellor Merkel to "restructure" Greek debt since Germans aren't inclined to pay for Greek transgressions. 

And that is exactly the problem with the Euro, no fiscal mechanism to buffer ideosyncratic shocks, as Joe Stiglitz forcefully explains.

In this instance I have always been with Joe Stiglitz (aka, the Euro was ill designed to work only in good times), and I am with Paul Krugman who highlights that there is really no way around Greece exiting the Euro. What I cannot figure out right now (since I am not a political scientist) is how important it is for EU politicians (especially those in France and Germany) to maintain the Eurozone status quo and how disasterous it will be for Greece to exit the EU in terms of contagion for Portugal and Spain.