World markets fell sharply Friday following a huge sell-off on Wall Street and amid fears that Europe's debt crisis could spread and derail the global economic recovery. At one stage, the Dow Jones industrial average was in freefall, trading 1,000 points lower.Investors around the world are uneasy about the prospect of trouble in the euro zone from Greece's crisis. Many economists say Greece may be insolvent in the end despite an EU-IMF bailout, and there are fears that other countries will worsen their finances in a vicious spiral. That could undermine markets and consumer confidence just as Europe crawls out of recession.