Crude oil prices started plummeting only two months after hitting a record high in July 2008, due to the financial crisis triggered by the collapse of Lehman Brothers. Speculators suddenly shifted their strategies from "buying" to "selling" in anticipation of weaker demand amid the global economic downturn. Although the price had fallen by as much as 70 percent by February this year, it has since been on the rise again.
According to the International Energy Agency, oil prices are likely to exceed $200 per barrel (159 liters) by 2030 — first, because oil reserves are finite and, second, because motorization is progressing with no end in sight in newly rising economies like China and India.
Once crude oil becomes that expensive, I believe its use will be limited to "noble uses" — petrochemical products mostly, because modern society cannot do without petroleum-based materials such as plastics, synthetic rubber, chemical textiles and polyethylene.