Today's Washington Post story on spread of nuclear programs across the developing world demonstrates the real danger of Iran's program. Despite the inflammatory comments of the likes of Ahmadinejad, the Iranians themselves, were they to develop nuclear arms, would be constrained by the doctrine of mutually assured destruction, just as every previous nuclear state has been. They would not be able to use their weapons on an enemy state -- Israel, for example -- without facing massive retaliation. They would not wish to give their weapons to terrorists or militias -- Hezbollah, for example -- for the same reason.
No, the real risk is that every regional rival, from Turkey to Egypt to Saudi Arabia to even the small gulf states, will have an advanced nuclear program from which it is only a short jump to nuclear arms. Mohammed ElBaradei calls it an "insurance" policy. I call it a need to fix the going-down-for-the-third-time Nonproliferation Treaty in a way that satisfies everyone... now.