In my average day I deal with people from five different countries, individuals in four different time zones, and have work shared between three different countries. These numbers add up to make me one very busy person walking what feels like an infinite amount of very fine lines.
Whatever your work is, especially if you're a progeek, odds are you are going to have to deal with people from many different countries and cultures. We are in a global economy (in case you haven't heard), the world is a much smaller place thanks to communications technologies, and with this economy, everyone wants a piece of the economic pie.
On top of all of that if you're in any kind of large city or development zone, like the greater Toronto area, the Baltimore-DC corridor, or Silicon Valley, then you almost certainly will work with people from all over the world. You may not be aware of it or think about it, but take a moment and ask yourselves about the backgrounds of your co-workers and clients.
What this means is that you'd better get culturally aware.