What about a new currency?
When the euro was created, there were no contingency plans for a country like Greece exiting the euro. But if that exit occurs, Greece will need to set up a new currency.
"Countries converted into the euro, so they ought to be able to convert out," Sagner says. "But how they go about doing that can be a very complex question."
Greece would need to decide on a name for its new currency and print and issue notes. But beyond the daunting logistics of implementing a new currency, Sagner says the Greek government also would have to revalue assets in the new currency. "That's where things could get ugly," Sagner says. "If a new Greek currency were allowed to trade against other currencies, you could see it losing about half its value."
In the meantime
Song remains optimistic that EU action will eventually quell market fears and preserve both the EU and the euro, at least for some countries. But the turbulence surrounding the crisis already has had a negative effect around the world.
"Whatever you think of the euro, the possibility that it might collapse, or even speculation about its collapse, is going to work against economic growth in Europe and our own economic recovery," Song says.
For Americans eyeing their 401(k)s and other investments, the wave of unpredictable news will hurt their bottom line, if it hasn't already, says Tony Zabiegala, vice president of Strategic Wealth Partners in Seven Hills, Ohio.
"If there is continued market volatility and no feasible solutions, stock market volatility around the world will continue," Zabiegala says. He adds that prolonged ups and downs also may weigh heavily on U.S. consumers who might be hesitant to spend money in the face of economic uncertainty.
But Americans don't have to passively watch their investments disappear with each market swing, says Mike McGervey, president of McGervey Wealth Management in North Canton, Ohio.
McGervey advises sophisticated investors to adjust to a less-aggressive portfolio and minimize exposure to Europe and to the U.S. financial industry, which is itself somewhat exposed to trouble in Europe. Less-sophisticated investors can check with their mutual fund company about their exposure to Europe.
"Some people might think that there's no difference between an aggressive portfolio and a moderate or conservative one because they all go down," McGervey says. "But really, it's a question of how much you lose at a time like this. The important thing is that consumers take action before the crisis, not after. (In 2008) a lot of people waited until we had hit bottom and then they sold their portfolios, which really didn't make any sense."