Some of this has to do with faulty investor logic. The euro was sold to investors in a way where they believed that once in the currecny there was no exit. So they tried to price all of the components the same, rather than pricing in soverign risk for each state. Or, in other words, if any investors pricied in sovereign risk others would be there to arb it out of the system.

I think for that there should be some mechanism to let the investors take the hit. The issue is whether or not the cost to bail out greece would be cheaper than to deal with the incremental risk premium on the rest of the eu debts. At some stage the tradeoff between economic logic and incentives (moral hazard) needs to be dealt with more transparently.