Consumption is not the same as production
The basic fallacy behind comparing PC use to oil consumption is that the model IS fundamentally different; PCs were (are?) subject to the "law" of mass-production: the more things that are made, the cheaper they become. Whereas oil production - from whatever source - is subject to supply and demand: the more something is consumed, the higher it's price becomes.
Now it might be convenient, as a prop for the "Rise of the ManufRacturers" to assume that:
> There's simply no shortage at all of shales to exploit around the world
However, that statement is clearly bollocks. Even if there was a (practically, if not physically) infinite supply of fossil fuel there is still geopolitical issues that limits its distribution: someone can turn off the tap - just ask Mr. Putin. There is also the factor of what to do with the emissions from burning this stuff: even if climate change is "questionable" now, once a proportion of this "no shortage" oil shale disappears into our air it will alter that questionability and/or lead to air pollution of unacceptable levels.
We could also discuss the effect of transportation costs (oil, being sucked out of the ground is, essentially, free. But the cost of getting it to the end user is high. Whereas PCs have substantial production / software costs and transport adds little to that) on the different markets. Also that PCs are not in themselves a desirable "good" - they are merely a platform for the software we wish to run on them and unlike oil don't have any viable alternatives for their use.