John Robb is not a proponent of terrorism and guerilla warfare, but he
is an astute analyst of it. Neither the White House nor the anti-Iraq
War folks are paying him enough attention, IMHO.

Here’s what he said recently about potential vulnerabilities of our current energy systems:

[Global Guerillas]:
A central theme of global guerrilla warfare is that the centralized
systems we rely upon in modern nation-states are unable to withstand
even a rudimentary low tech assault.  The environmental movement
picked up on this vulnerability for their own purposes.  Their
message:  clean energy is more secure energy.  This is
accurate.  Clean energy requires decentralized production and is
by its nature more secure….

Eco-terrorism isn’t new.  It is, however, typically ineffective.  This report [Cascadia Scorecard] points to another potential scenario.  If eco-activists adopt global guerrilla tactics,
they could coerce a rapid move to clean energy alternatives. 
Small but extremely effective (high ROI) attacks on the energy
corridors leading to target regions, would quickly increase the costs
of conventional energy such that clean power alternatives would become
extremely attractive.  This would be dictated by a direct economic
comparison (costs) as well as indirect factors such as reliability of
delivery.  This systems sabotage tax would induce a tipping point
in energy market equilibria towards green alternatives if it is
extended over a long period (longer than one season) and is of a
sufficient level.  See the brief
Urban Takedowns for more on how a terrorism tax can impact market equilibria.