Peak Oil is a real, immanent, and very serious problem. It is nothing like Global Warming at all. Here's why.
While there may have been a point in time when the Global Warming hypothesis merited some attention (back when the issue was first mooted, perhaps), subsequent years of sober and rational reflection have shown us that those concerns can be safely dismissed. Mankind simply cannot produce enough carbon dioxide to affect the climate. The scale is too vast, the feedbacks are too complicated, and the other forcing and/or buffering mechanisms we have identified completely swamp whatever paltry effect our miniscule contribution to global greenhouse gas levels may be causing (if there even is such an effect, which we cannot definitively conclude).
On the other hand, the lexicon of alarmist terms with which we have become familiar through the Global Warming debate -- terms like 'tipping point' and 'runaway feedback' -- really do apply in the case of Peak Oil. Just one Iranian nuclear weapon, whether or not it is even detonated, could set off a chain of events which will disturb the world's oil-producing region for the foreseeable future.
There is a human dimension to this problem which most commentators seem oblivious to. Oil in the ground does nobody any good. If it cannot be extracted, bought, sold, transported, and refined into useful products, it might as well not exist. It is human societies which produce and consume oil, and our ability to exploit a resource is conditioned by numerous factors besides the level of stated reserves. You cannot simply assume that we will have the resources and finance capital to utilize unconventional oil sources. You cannot simply assume that "technology" is a silver bullet which will overcome all production hurdles. And only someone blissfully ignorant of all world history could believe that governments will ever "get out of the way" and allow private oil producers to pump the wells dry in a Libertarian fantasy-land. The world is the theater of bloody politics: it always has been and it always will be. People will fight for power, wealth, and security, and many delicate fruits of our exigent civil society -- fruits like easy access to finance capital and loads of money for R&D -- will get trampled in the process. The system of intellectual and financial tensions stretched across the global economy is now so tight that any minor supply disruption could cause the threads to begin to snap. And with the world's advanced economies getting older and deeper in debt, they will not be able to consume oil as efficiently as before. This is just the beginning of a process that will result in a slowdown of the global economy and the outbreak of hostilities. We will have to get used to living in a world where war is more frequent and wealth less taken for granted; a world, in short, of less civilization.
Ultimately, it is man's ability to produce and consume energy efficiently which has peaked. This is the critical measure, the only one that counts in the last analysis. It has a complicated relationship with resource reserve levels, but is not linearly dependent on them. It is more dependent on culture, on the societal discipline which develops the talent necessary to rule the world with the force and intelligence that such requires. The West began depleting that resource quite some time ago.