We need to develop clean, renewable sources of alternative energy. Oil CAN be synthesized from biomass. Clean, green fuels CAN be developed. The Fischer-Tropsch process has been around for a long time. Fuel cells are becoming economical.
Natural gas is clean and renewable because it can be generated from biomass.
There are alternatives everywhere. Furthermore, any power center is a tempting target. The World Trade Center. The Oklahoma City federal building. The North American electrical grid.