Spynverzyon:

… when you make something more expensive, people will indulge in it less. The point of bombing Iran’s nuclear and petroleum facilities is to make their political and military aggression expensive, thereby giving them incentive to do less of it.

As the war on terror has become more expensive (in terms of financial and human cost), does that mean that the US has “indulged” in it less? I would say no, that the commitment remains in place (at least in the executive branch) despite the rising costs. Clearly there are factors other than financial expense at play; and I would guess the same applies in Iran’s commitment to nuclear capability.

Would the Shiites hate us forever? Probably not any more than the Japanese do. The Shiites can afford to hate us now because it costs them little to do so – indeed, it is often profitable for them.

That’s a glib and facetious comparison; “the Shiites” aren’t “the Japanese”, and this isn’t World War Two. I don’t even understand what you mean by the “Shiites can afford to hate us now because it costs them little to do so,” as if hate is determined on a cost-benefit basis.

Would disruption of the oil supply raise the worldwide price of oil? Undoubtedly, but not nearly as much as the price would rise if a nuclear Iran gained hegemony over its Gulf neighbors.

A fair point, but your thinking appears to be either that we bomb Iran or they become the hegemonic power in the region; I’d suggest that the situation is probably a bit more nuanced than that.

Would the Iranians become more secretive about their nuclear research?… But even if they went underground, the costs of doing so would, again, make their nuclear activity more expensive – meaning they would do less of it.

See my point above. This is not just about financial cost for Iran, a country that fought an eight year war against Iraq at a cost of 1 million casualties and over $300 billion. Do you really think that they’re going to throw their hands up and go, hey, this costs too much?
Incidentally Iran is one of the few countries in the world to actually have had WMD used against its armed forces and civilian populations in a war, but of course we don’t hear much about that these days.

As for joan’s perspective, the Iraqis did greet us with cheers (if not flowers) at first – until the concerted efforts of the American left, for whom winning the war would have meant political disaster, so constrained our will that our overall strategic plan lost credence.

Can you present any evidence at all that the “American left” had anything to do with constraining “our” will? And any evidence that the “credence” of the overall strategic plan was of any interest whatsoever to people in Iraq?
I arrived in Baghdad four weeks after the deposal of Saddam. The first question I asked my driver was, “What do people think about America?” His answer – repeated many times over the next few weeks in my conversations with other Iraqis – was “We are very happy that they have removed Saddam, but we hope they leave very soon.”