When the Swiss franc hit a historic high of buying .70 euros in May 2010, people lined up at a Geneva exchange office to get rid of their euros. This week, one Swiss franc bought .90 euros. Fabrice Coffrini/AFP/Getty Images hide caption

itoggle caption Fabrice Coffrini/AFP/Getty Images

When Canada switched to dollar coins, or "loonies," its simply took the country's dollar notes out of circulation. The GAO says the U.S. needs a similar plan. Ryan Remiorz/AP hide caption

itoggle caption Ryan Remiorz/AP