Many believe the likelihood of a euro breakup is somewhere between a significant possibility and a dead certainty. Domenico Lombardi of the Brookings Institution recently set the chances at 50-50. Jeff Wallace, managing partner at Greenwich Treasury Advisors, goes further: "It's pretty close to 100% probability—the only question is when." A breakup could take three forms, experts agree: a complete disintegration of the euro, in which all countries revert to a domestic currency; an orderly breakup in which weaker countries such as Greece, Portugal and Ireland can opt to exit the euro; or an exodus of stronger countries to create a new currency.

The second scenario is seen as most likely, although certain hurdles would need to be overcome.

"Currently, there is no mechanism for members to expel a country because of default or a formal mechanism for a country to leave the euro," says Trevor Williams, chief economist of Lloyds Bank Corporate Markets. "But this does not mean that it cannot happen."