Sucked into a Black Hole

At night, the streets of Phnom Penh reveal the country's vast wealth gap. In front of shopping centers selling luxury cosmetics, whole families sleep on patches of sidewalk; beggars missing limbs, a legacy of civil war, crowd outside upscale restaurants where a tiny élite downs French entrées and chic cocktails. But many average Cambodians hope this poverty will vanish, thanks to an apparent miracle: the country has discovered oil. Off Cambodia's southern coast, explorers have found as much as 500 million barrels, potentially providing over $1 billion annually to the country.

Cambodia is hardly...