@MontereyJack,
What Obama meant when he said, "you didn't build that" is the simple fact that without the developed infrastructure, our economy (and all other developed countries) would come to a stand still. Roads, highways, bridges, communication systems, airports, railroads, utilities, and all the services that governments provides are all necessary for any economy to operate efficiently.
Without any of these infrastructure, no business will be able to thrive or exist.
Many people fail to understand simple Econ 101 principles.