When is a million idling computers good for the planet?

Leo Hickman of The Guardian poses this question.  IBM’s World Community Grid, a network of more than 400,000 computer users who own more than a million computers, has volunteered to pool their collective computer power to help a Harvard’ chemistry team discover an organic material that may pave the way for a less expensive and more efficient solar cell.  In this case, most would agree that the payoff is worth the potential gain — but it’s a slippery slope:

At some point, our most essential services will need to be given priority when it comes to dishing out the remaining fossil fuels equitably. In theory, this will start to price out “non-essential” uses of such fuels.

But who is going to draw that line between essential and non-essential use? What, for example, would you place into the “essential” trolley? Two thousand miles’ worth of petro-fuelled driving a year? Enough energy to heat your living room to 18C during winter?

Given that we each lead very different lives, should each of us have a “free” minimum allowance for such essentials?