The most used tool in every decision, business or in a day-to-day situation is the cost-benefit analysis. Accordingly, if benefits are greater then costs that means I'll have profit and I will put in practice that idea or that plan. The reverse situation will bring a loss, so I have to avoid it by all means. It is simple.
Maybe the amount of money that are required for save Greece is (yet) less than amount of money that will be required by too-big-to-fail banks in the case of Greek default.
What is the worst case scenario in the case of default? The Greek default is postponed only because this year many Euro-states will have elections? And many other questions are on the Internet. They have two aims: firstly, to test some scenarios and their possible outcomes on the public opinion. Secondly, to test few levels of social indicators like the current state of public perceptions about political decisions, like the level of public awarness of a possible economic impact of various decisions, and so on.
My opinion is that things are more controlled than they seem to be. If the Greek behaviour will be changed by some austerity measures, there will be some hopes to keep Greece in the EU. However, the current facts haven't a positiv impact on international public opinion and it's a matter of time until Greece will be get out from the EU.
And this is the worst case scenario for the Greek people on the short and medium term. A return to the Drahma could represent a big inflation and a lower standard of living for few years, maybe a decade. In the long term view, all depends on international economic climate.