The fear of Greece leaving the single currency (Grexit) has been a recurring theme since the collapse of Lehman Brothers. The country has only remained within the Eurozone via multiple bailouts from the IMF, otherwise the country would have defaulted on its commitments and been forced from the currency union.
At the latest election, the citizens of Greece voted for the anti-austerity Syriza Party which are playing hard ball with Brussels as the country verges on bankruptcy. The leader of Syriza, PM Tsipras is attempting to revoke the previous austerity measures at the same time as ensuring the next tranche of bailouts from the IMF. As reported by Bloomberg, the Bond markets are betting on a Grexit, as the uncertainty over the Greeks future continues.
The Greece uncertainty has been pushed along, by short term agreements, without any long lasting agreements. The amount of cash that the country actually has is unknown, and at what date the country would be bankrupt. The media is discussing how things could play out from hear with the likelihood of capital controls, to slow capital fleeing the country.
Brussels and the IMF do not want to set a precedent with Greece, as the renegotiations on debt would likely follow from the other members of the PIGS (Spain, Portugal and Ireland).