Stewart Brand addresses The Long Now Foundation on Cities and Time.
Cities are humanity's longest-lived organizations (Jericho dates back 10,500 years), but also the most constantly changing. Even in Europe they consume 2-3% of their material fabric a year, which means a wholly new city every 50 years. In the US and the developing world it's much faster.
Every week in the world a million new people move to cities. In 2007 50% of our 6.5 billion population will live in cities. In 1800 it was 3% of the total population then. In 1900 it was 14%. In 2030 it's expected to be 61%. This is a tipping point. We're becoming a city planet.
One of the effects of globalization is to empower cities more and more. Communications and economic activities bypass national boundaries. With many national governments in the developing world discredited, corporations and NGOs go direct to where the markets, the workers, and the needs are, in the cities. Every city is becoming a "world city." Many elites don't live in one city now, they live "in cities"- The Long Now Foundation