There's a long, but thorough, well sourced and well reasoned post on the idiocy of considering a war against Iran at the Belgravia Dispatch:

And then there are the possible Iranian responses. Anthony Cordesman spelled a few of them out recently, and they include (his language, with slight B.D tweaks): 1) Iranian retaliation against US forces in Iraq and Afghanistan using Shahab-3 missiles armed with CBR warheads; 2) using proxy groups including al-Zarqawi and Sadr in Iraq to intensify the insurgency and escalate the attacks against US forces and Iraqi Security Forces; 3) turning the Shi’ite majority in Iraq against the US presence and demand US forces to leave; 4) attacking the US homeland with suicide bombs by proxy groups or deliver CBR weapons to al-Qa’ida to use against the US; 5) using its asymmetric capabilities to attacks US interests in the region including soft targets: e.g. embassies, commercial centers, and American citizens; 6) attacking US naval forces stationed in the Gulf with anti-ship missiles, asymmetric warfare, and mines; 7) attacking Israel with missile attacks possibly with CBR warheads; 8) retaliating against energy targets in the Gulf and temporarily shut off the flow of oil from the Strait of Hormuz; and 9) stopping all of its oil and gas shipments to increase the price of oil, inflict damage on the global and US economies.

Yes, we can game plan for some of these contigencies and take preventative action. But, lest we forget, we have a gross incompetent at the helm of the Defense Department, so chances are he'll make a mockery of a good deal of the war-planning.

I don't have anything to add. There's lots more, and it's all very thoughtful. This guy is, btw, a conservative McCain supporter. Thinking people are fleeing the sinking ship, regardless of political affiliation.