The Fitch Ratings agency expressed concerns over the absence of any credible financial backstop. Fitch is concerned that the ECB's commitment to provide liquidity during a liquidity crisis is not active and explicit enough. Click "Fitch casts doubt on European plans to stop crisis" to read the full AFP article, whom I acknowledge.
The next of many possible scenarios to consider are: that Germany leaves the Eurozone, damaging German exports to devalued Euro currency nations; or Greece leaves the Eurozone, threatening French and other banks exposed to Greek debt. But there are more possible outcomes than can be enumerated. See also: "Beating a path to a Euro break-up"; "Draghi warns on eurozone break-up"; and "ECB's Stark discusses resignation", the latter of which describes how the core of the Eurozone conflict is agreement upon the purpose of the ECB.