True, and I tend to underestimate just how centralized the production of a lot of things are, since what I do isn't really based that heavily on geographic location.

My counter to that, though, is that there is usually at least a couple of producers of most products, and that sometimes -- though not always -- they are geographically separated enough that the risk is somewhat mitigated. Other times, though, geographic constraints sort of mandate that every supplier be located within a small number of miles of one another; suppliers of natural resources (coal, oil, etc) come immediately to mind.