But that line could change.
Psychology played in the Great Recession which magnified it after the math failed. No one trusted each other and banks borrowed from each other with credit asset swapping. (Why weren't they labeled expenses??)
So viola they all told each other you are no good. BOOM! Collapse and Uncle Sam had to come in and payback and buy the junk assets to try to have them trust each other again.
If Greece goes Italy will be viewed next (bad side). If they go fear will spread and those like Portugal WILL get shafted as investors know no one else will pay for their bonds so if you buy your money will be out the window etc. The bonds are worth as much as toilet paper as no one will buy them due to fear.
Yes this sounds nonsensical but in the great recession, 1929, and other events in history it has happened. I doubt banks hold less greek bonds unless the IMF bought them all? Why? Let's say you own them? Who in their right mind would buy them?! No one. You are stuck holding them or selling them at a HUGE loss.