Retired General and former CENTCOM CINC John Abizaid argues that we could live with a nuclear Iran. And, indeed, we could. Iran getting a nuclear bomb wouldn't be a threat to the United States and wouldn't even be an especially serious problem for Israel or any aspects of American power projections in the region.
Somewhat ironically, I think getting clearer about this might make it easier to prevent Iran from getting a nuclear weapon. Acting in an unduly paranoid manner about the Iranian nuclear program suggests to Iranians that there are some large gains that might accrue to their country from developing nuclear weapons. In fact, a nuclear weapons program would be a largely useless waste of money. The United States has good reason to worry about nuclear proliferation in general and, therefore, to worry about the Iranian program as an instance of the general phenomenon. But Iranian nuclear weapons, as such, aren't a big problem for us.
Photo by Flickr user Hamed Saber used under a Creative Commons license