the 'leave the euro-zone' and default on national debt solution doesn't do much... well actually it massively helps greece in the short term - internally inflation is not caused by over-spending, austerity measures are not needed to pay off debt - however inflation is caused by capital flight (and until that inflation balances out, ie whenever investors 'trust' that the greek economy has hit rock bottom, the capital flight continues...
of course there may be a possible option which includes controls on capital flow (i'd suggest a rate limiting effect, something along the lines of $ per day in/out of the system limited to some percentage of GDP) but with massive capital flight you may need internal lending systems to get the economy moving (or large-scale printing of money, which will push the inflationary pressures)
the positive for greece is that all of these problems become short-term issues.
Great, except for the people who the greeks owe money to, every bank and euro-loan not paid back undermines the banking systems (and due to nationalization of private banking debt the governments) of the rest of europe. The whole systems loses confidence, facilitating more capital flight, and lose of value of the Euro on the international exchange... (which will eventually make all european exports pickup, as the price of european labour drops below that of chian/india... but that's a long time-a-waiting.... and in the mean time Germany has a huge economic advantage over the austerity countries - leading to terrible inequality, and further break-up of the euro...)
So instead we're not going to do that, we're going to appease the non-german nations by bailing them out again.=> reduce inequality => reduce instability => fail to provide confidence that this is even possible => slip further into recession...