Thomas Friedman gets 2 out of 3.
He rightfully hammers bush mouthpiece dana perino, acknowledges that wars ought to be paid for in real time and then continues his support fo the Iraq debacle:

Of course, the chairman of the House Appropriations Committee, the Democrat David Obey, in proposing an Iraq war tax to help balance the budget was expressing his displeasure with the war. But he was also making a very important point when he said, “If this war is important enough to fight, then it ought to be important enough to pay for.”
The struggle against radical Islam is the fight of our generation. We all need to pitch in — not charge it on our children’s Visa cards.

How should a war be financed?
Setting aside for now the moral absurdity of this question lets get to the answer.
Taxes of one kind or another are the pretty obvious method. You either reallocate funds already being collected or you add new taxes. In the case of Iraq and Afghanistan there are no funds to reallocate so additional taxation is required. But who should pay those taxes?
A number of suggestions have been proposed for obey’s war tax. For example, Mark Thoma says:

I don’t think that now is the right time to raise taxes given the weakness in the economy,…
…what if the rich and powerful had been told that their tax cuts would have to wait until the war ended, …
Being forced to pay for a war I don’t support would tick me off, but that’s the point — by making the public fully internalize the cost of the nation’s decision to go to war (including the human cost), it will motivate more pressure to bring this war to an end.

Sounds pretty much like a take back the tax cuts argument which implies that whoever received the benefit of the bush tax cuts should pay for the war. Mark wavers on paying for the war now because of weakness in the economy but it seems that that is part of the point of those that argue that the war would end if the costs were internalized. On the other hand if Hale Stewart is correct about the real source of the economic strength of the past few years then Mark’s argument re the economy’s current weakness may not be that strong.
Mark should be ticked off anyway. He and his kids are paying for the war one way or another just like the rest of us.
Ron Beasley provides a a slightly different target for a war tax:

I have thought for some time that the quickest way to end the war would be to add a surtax to the incomes of the top ten percent, the bloated oil company profits and the profits of the largest corporations. These groups would be ready to pull out in no time.

He is exactly right that a surtax should be imposed. He and Mark are both exactly wrong on whom it should be imposed.
The only even marginally ethical method of paying for a war is for those who support the war to pay for it. Yes, only those who support the war and no one else no matter how small or large their income.
The mechanism should be relatively easy for the IRS to set up:

• Either by mail or online you periodically tell the IRS that you support the war (it shoudl be opt in) though governments and business prefer opt out
• The war costs $x for a collection period
• The estimated taxable income of the war supports is $y for the collection period
• Each supporting tax payer pays $x/$y % of their estimated income each collection period; before deductions

No progressivity. If you are going to support a war you pay for it.
What might the impact be. Well, in 2006 personal wage and labor income(pdf) was $6.989 Trillion. If 50% of this income supported the war a 6% surtax would give the bushies about $210 billion to play with.
If only 30% of the income supported the war a 10% surtax would generate $210 billion. There is no excuse for not making the war’s supporters pay.

There is also no excuse for the Iraq war. It would probably have ended a few years ago. If it even managed to get funding to start!