http://www.aviationnow.com/avnow/news/channel_awst_story.jsp?id=news/aw091106p1.xml
[excerpt:]
The Iranians purposefully have not followed Iraq's 1981 model of concentrating their nuclear development in a single area. They have distributed their nuclear development over numerous sites, including Bushehr, where a nuclear power plant is being built. Natanz is the site of a pilot fuel enrichment plant, and where a full-scale facility is under construction. Arak is the site of a research reactor and a heavy water production plant inaugurated in August.
While the multiplicity of sites makes drawing up a comprehensive target list more challenging, U.S. and Israel officials also suggest there are positive aspects to this. Not every nuclear-related site need be struck to hobble any nascent nuclear weapons program. The goal would be to select a few choke points.
"There are lots of links in the chain you can attack," says a former senior Israeli diplomat. "So how you define the mission is important. There may be 40 facilities [the total may be considerably higher], but you select only four. You don't have to attack all of them. For example, some targets are vulnerable to movement, like centrifuges. They need stability, so if you create enough [vibration or Earth tremors], their alignment can be distorted."
As the system expands or changes over time, additional small-scale attacks could further delay the effort, whenever it approaches a critical stage of development. While Israeli officials do not believe an Iranian nuclear weapons program can be stopped, they are convinced it could be slowed by years with the idea that time, negotiations, sanctions and perhaps changes in government could alter the desire to arm.
And there is an immense difficulty in assessing that in a closed political systems. Saddam offered little, Pajamaman won't either. Don't bet on the IAEA...