> But holding the debate hostage with demands for ethical impossibilities is somehow okay?

It's not an ethical impossibility. It's a pragmatic imperative. AND it's the root of the entire conversation. It's what I started this comment tree about! How can it possibly be holding up the debate to talk about it?

> b) Some other, smaller, amount along with a list of the effects you have discounted from the full amount and justification for such discounting.

Well it's certainly got to be this one since reversing every effect is entropically impossible. Some obvious things I don't really care about are restoring BPs bottom-line to its pre-disaster levels. As a general rule I'm also not interested in paying to mitigate damage to wildlife that would fall under ICUN's Least Concern designation (http://en.wikipedia.org/wiki/Least_Concern) even after all harm to populations from the spill are taken into account. I feel this way except inasmuch as human beings depend on such wildlife for economic sustenance. Although it sucks that the animals die, if they are not used directly by humans the utility lost when a common animal dies is typically far less than the cost of saving it in an oil spill like this.

Endangered animals I do want to protect, but once again there's a line somewhere (I don't know where) where their protection costs more than its worth. For example, if there is a rare mosquito in the marshes of southern Louisiana that ends up being wiped out entirely because of this crisis, I would not assign a cost of a billion dollars to that lost. Some cost, yes, but not a billion dollars.

If the oil slick bears out to be very large but cause small or questionable harm across a huge region, I also don't think we should necessarily spend money compensating the victims of such small harms. (For example, even if the oil spill stopped now some amount of oil would probably disperse even as far as the west coast of the U.S. after enough time.) To assign a metric, if the amount of compensation we might provide to a given victim is less than ten times the administrative cost of giving that compensation, we should not compensate.

Looking at the worst case scenario: let's say that the entire gulf becomes unfishable for the next fifty years except if the U.S. spends a quarter of its total output during that time period cleaning it up. Obviously this would be a really bad trade because the fishing in that region accounts for a much smaller portion of GDP than a quarter. BP should have to pay to support the people in that region, but realistically even the profits of an oil giant like BP would quickly be quenched under such a deluge of liability. Maybe the government can help them move and pay for their retraining, but in the end there is no point throwing good money after bad. They would need to do something else or maybe relocate to another place.

Obviously all these numbers are sketches. I can hardly tell you what the actual numbers are (if you'll recall, my initial comment was a request for speculation on what that number might be). But there is no question that there is a number, or a range of reasonable numbers, to describe the cost of this disaster.

> Alternatively, you can be gracious and concede the point that if there are alternatives to high-risk offshore oil wells . . .

That is not even a point under discussion. Why did you bring it up? What makes you think I support offshore drilling? We are talking about whether it makes sense to assign a numeric cost to the disaster, which it obviously does.