It's easy to dismiss this issue with a "garbage in, garbage out" joke, as I've heard lots of people do over the years, but the core issue is that if you're constructing any non-trivial model of all or part of the world energy market you're forced to make a buttload of guesses and assumptions.

Spooky is right on the money with the comment: "Of particular concern is the accuracy of Saudi and other ME reserve numbers."  The problem is that lacking good data we have to choose between trusting the SA numbers or coming up with our own.  The first seems inherently naive, while the second leaves us with a humongous question and no good way to answer it.

I agree that the above-ground issues will be extremely important in coming years.  Many PO adherents like to say that in PO we're facing a unique event in human history.  I agree with that view, which is precisely why I think that the human element--public policy, war, market psychology--will play a (much?) larger role in the energy markets than they have in the past.  Frankly, I don't see how anyone can talk about how serious the arrival of PO is without coming to that conclusion.

And, of course, an increased role for human affairs and reactions makes the process of accurately predicting anything about the energy market all the more difficult.