This week's Miami Art Basel, the world's most important art fair and normally a scene of champagne-soaked excess as wealthy art lovers convene to outdo each other on spending tens of millions on star artists, has a gloomy cloud over it as the art market experiences a dramatic dive. The hedge funders probably won't be snapping things up—even those who haven't been crushed in recent months are likely to deem big spending unseemly—while buyers from the emerging markets like India, the Middle East and China, who had recently swelled the ranks of serious collectors, won't be making an appearance.