I believe the mass default scenario in Europe that many are preparing for is a highly unlikely outcome. It is not in anybody's interest for there to be mass insolvencies in Europe and for the continent to slip into a depression.
Greece has been playing a game of chicken with the EU, thinking that the EU cannot let them go. While reforms have been passed, they have not been enforced. If Greece does not reform itself than there is no point to the bailouts. The EU is being left little choice but to let Greece go. At best Greece might get one more chance but I think the decision may have been made already.
Most of those who are opposed to bailing out Greece do not feel the same way about the rest of Europe. In the rest of Europe reforms are being made and commitments are being met. Even those opposed to bailing out Greece believe that the rest of Europe needs to be ring fenced in the case of a Greek default. German politicians who are opposed to the Greek bailouts have said so. Nobody is supporting a Lehman style bankruptcy where one day Greece goes under and nothing is put into place to stop the collateral damage. It is likely that those countries who accept bailouts will have to give up some of their sovereignity and submit their budgets to the EU for approval. But it seems like an easy choice.
I believe that Europe wants to vote the EFSF into place before they let Greece go so they have a mechanism to stop the collateral damage. Its unlikely that there will be a giant wave of mass insolvencies and depression. Nobody wants that. Markets over react and I believe they are placing a much larger chance of the disaster scenario occurring than is likely.