I think that's putting a bit too much emphasis on proving a negative though. The only way to prove, within reason, that something that was created no longer exists, is if you first of all have detailed records of its creation, but then also more importantly of its destruction. Once the records are compromised that possibility is virtually out the window. So what you're left with then is whether or not it's reasonable to suspect something is left behind. Blix, as far as I recall, said he needed a few more months to complete his mission, but that he so far had not found anything that amounted to the weapons the coalition was talking about.
I think we also should remember that from the standpoint of the average American or UK citizen, even where Saddam was when he ceased his WMD program he didn't pose an immediate threat to those citizens. So the worst case scenario would really have been that Saddam not only kept WMD but somehow managed to create a delivery system capable of reaching these nations. That's an even taller order to fill in terms of evidence.
So in my opinion the issue wasn't that Saddam was a bastard that had to go one way or another, sooner or later, but whether or not going to war at that time using the arguments that were made was reasonable As far as I can see, as the evidence was lacking, the correct thing to do was to wait. If the inspectors had been given more time they would have reached the conclusion we are now all aware of. But if Saddam would have prevented them from doing their job again the option of attacking still was there. And there'd have been a better case to bring to the UN for a resolution and better basis for it.
On a different note: John pointed out a while ago that it's a basic problem how we "deal with" these sorts of dictators. I'm personally torn between whether or not other nations should intervene or not. You (I think) made the point that countries may be more reluctant to do so moving forward and I flippantly replied that we'll have forgotten about it soon enough. I still think that's the case, but your point isn't really something I disagree with in one sense; should we intervene and at what cost?
From what I can see stability seems to come mostly when nations have their borders drawn along lines the people in the region are ok with, as well as when they feel their leaders represents their views. So in the case of Romania the people changed their own country. Out with the dictator, in with something better. Peace. Stability. Iran, same thing with Mossadegh really. Out with the Shah, in with a democratic system. Unfortunately external meddling made that unravel. So on the one hand I can see the point you implied earlier which I'd paraphrase as that we perhaps need to deal with some regimes before things get worse not only for those who can't deal with it themselves but also for us, but then on the other I have to be skeptical when it comes to the true intentions of our leaders as well as the ability to actually be able to get to a decent solution without possibly breaking up nations (i.e. the Kurds get independence, and the Sunni / Shia might split as well, etc).......
What are your thoughts on the latter?