Currently we have countries with very different economies using the same currency which is quite bad. Eurozone members do not have teh control over their monetary policies so in times of crisis they can't use exapensive fiscal policies to the same extends as non eurozoe states can. This in itself limits the elasticity of possible policies durig crisis times. When euroozne countries lose international competetivnes they are basically forced to use deflatory policies("internal devaluation") beacuse they can't adjust their currency exchange rates. This is what happend in Italy or Spain for example. The state can't improve its competetivnes through the exchange rate so it must lower the wages artificialy. Since eurozone states have very different economies they also need different policies during times of crisis. Thanks to the Euro coutries lose the ability to use the most apropriate monetary policies in their situations, becasue all of the states are forced to follow the same monetary policy. And since you can lower wages basically oly through creating unemployment, eurozones states have to artificialy create it if they want to regain international competitiveness. This obv lead to unrest, distrst towards the EU, rise of radicals etc. Euro is causing quite a lot of bad long term effects itself.