Yes, we will eventually run out of oil. Or, more accurately, extracting oil will eventually cost more than we're willing to pay. But there is not one price where we all decide it's not worth it. It's already too expensive for some uses, and inexepensive enough for others. But the most important point is that we don't need oil, we need energy .
Oil is simply the cheapest way to get energy at the moment.
The point isn't that diminishing supplies is not a problem. But it's a problem we can solve by finding alternatives. Free markets give incentive to develop alternatives according to how much we think we need an alternative, and historically we do tend to work these things out. A draft version is available free online . I love the icons on the Software Carpentry site.