"Petty crime and pollution are common inconveniences in cities big and small. But in megacities, those with a population of 10 million or more, these and other everyday headaches can quickly become mammoth problems-putting both lives and treasure at risk. The stakes have never been higher. In 1995, the world had just 14 megacities. By 2015, there will be 21. FP looks at the problems plaguing six of them."