Europe is fretting over Greece. While the future of the EU and the Euro may indeed be at risk, the bigger concern probably actually relates to the exposure of French and German banks and their governments to a possible Greek default. The citizens of Europe might be even less likely to support what is actually a French/German banking bailout than a Greek bailout if this aspect is highlighted. Take a look at the chart below.
If Greece defaults, then a banking bailout would be almost a certainty. Otherwise, a domino effect would probably take down the world's whole banking system. So the choices are: 1) Bailout Greece (again and again) or 2) Let Greece default and bail out the banks instead. Neither seems to be an attractive option when considering the likely backlash from voters.
