One of the most unappreciated aspects of our global economic system is the ability of small groups, typically driven by greed, to severely disrupt it.
The oil crisis, that drove prices to nearly $150 a barrel, was due to a combination of a tightly coupled global economic system with a 2 million barrel a day shortfall in supply due to growth in Chinese demand. That production shortfall was the result of systems disruption. Small groups of guerrillas in both Iraq (~1 to 1.5 million barrels a day) and Nigeria (up to 1 million barrels a day) routinely blew up pipelines, mostly for personal profit. The oil spike drove up costs to unacceptable levels for stretched American households. This resulted in a spike in defaults on subprime mortgages as the economy slowed and marginal household budgets failed. In parallel a relatively small group of financiers concentrated in a score of companies, added egregious instability into the global financial system (excessive debt and leverage + "too complex to understand" derivatives) for personal profit. This unstable system amplified these subprime mortgage defaults (a relatively small slice of total debt) into a global financial crisis.
Nothing has changed. Much more of this behavior is on the way. For a more complete preview of how this is done, read Brave New War. I wrote it with the intent that it would eventually be viewed as the first installment on a definitive manual for 21st Century conflict.
PS. Being an occasional mercenary, in 2004 I spoke to a dozen huge hedge funds in London (individually) about how the dynamic of small group disruption + extreme global system leverage would drive up oil prices to astounding levels. Those that headed this advice, made tens hundreds of billions of $$.