If Greece defaults, most likely they will exit the Eurozone and this will be disastrous for Europe (Italy and Spain will be exposed in particular).
Financially, it will send a ripple effect and the Euro will devalue as those debts can't be collected, i.e. written off. Politically, it will be the beginning of the end of the Eurozone.
Again, basic knowledge of the current public opinions of either countries on the subject strongly indicates the contrary.
I do not have the background required to have an informed opinion about the economical consequences of such situation.
Just stating the obvious from a pure political standpoint IMHO.
In Greece's situation, the public opinion (by form of referendum) is used to cement their bargaining position, i.e. the people are ready to accept the repercussions of debt default if they don't get a better deal.
Which is why the negotiation is continuing / will continue, otherwise it will be a terrible lose-lose situation for all.