In this piece for New Geography, Kotkin writes that for all the positive aspects of these urban conglomerations there are many more terrible conditions that make these types of places undesirable.
"[E]ssentially megacities in developing countries should be seen for what they are: a tragic replaying of the worst aspects of the mass urbanization that occurred previously in the West. They play to the nostalgic tendency among urbanists to look back with fondness on the crowded cities of early 20th Century North America and Europe. Urban boosters like the Philadelphia Inquirer's John Timpane speak fondly about going back to the "the way we were" - when our parents or grandparents lived stacked in small apartments, rode the subway to work and maintained a relatively small carbon footprint.
Unfortunately such places were often not so nice for the people who actually lived in them. After all, they have been moving from higher to lower density locations for over fifty years, a trend still noticeable in the new Census."