The main problem with the Euro is purely its value. Due to the ever increasing number of economies joining from poorer (mainly ex eastern bloc countries such as soon to be Poland), it pushes the value of the currency up and therefore the GDP of that country adds value to it. Now this creates a problem when you consider prices of goods will also increase to the rate at which the Euro trades. Then because a lot of companies who had a base in those countries lose their cheap labour and it pushes prices and wages sky high, they move simply to another country (Asia nowadays). This then causes unemployment and as a result the Government is usually forced to borrow more to support the ever growing population out of work, as well as investing into the numerous (and often pointless) EU funds for this and that. Countries like Greece, Portugal, Ireland etc. have never ever been on the same comparative level of production and economic success as Germany or France. As such it is doomed to collapse under its own weight as the Germans and the French will have to support the weaker parts of the economy.
Think of it like an empire. You have a war on 3 fronts, which is highly disastrous. You are losing thousands of men each week, what can can you do to keep hold to those territories desperately? Send more men to the front line. This is basically what Germany is doing with it's Euro empire, and whoever argues that Germany is not the dictator in this all to the rest of Europe is clearly dillusional. It is trying to buffer up its interlinked economies on the furthest reaches of Europe and is failing because those countries cannot meet the same standards as one another. All empires must fall, maybe even the German dominated Eurozone will too, The Roman Empire did after all. History will repeat itself. The Eurozone is far too over stretched to handle problems now, and any decision has an impact on the other 16 members. They should have left it at its original number.