First we got the bomb, and that was good...

Rico says the post title comes from an old Tom Lehrer song called "Who's Next?" that continues "...because we're for peace and brotherhood; then Russia got the bomb, but that's okay, because the balance of power is maintained that way". It then lists the others who either have it or want it (France, China, Indonesia, South Africa, Egypt, Israel, Luxembourg, Monaco, and Alabama). But Iran? Not such a good idea, though Adam Lowther makes an interesting case of it in a column in The New York Times:

With Iran having notified the United Nations nuclear watchdog agency on Monday that, any day now, it will begin enriching its stockpile of uranium in order to power a medical reactor, we should admit that Washington’s approach to countering the Islamic Republic is leading nowhere. What’s needed, however, may be less of a change of plan than a change in how we view the threat of a nuclear-armed Iran. Believe it or not, there are some potential benefits to the United States should Iran build a bomb. (I’m speaking for myself here, and in no way for the Air Force.) Five possibilities come to mind.
First, Iran’s development of nuclear weapons would give the United States an opportunity to finally defeat violent Sunni-Arab terrorist groups like Al Qaeda. Here’s why: a nuclear Iran is primarily a threat to its neighbors, not the United States. Thus Washington could offer regional security— primarily, a Middle East nuclear umbrella— in exchange for economic, political, and social reforms in the autocratic Arab regimes responsible for breeding the discontent that led to the attacks of 11 September 2001.
Until now, the Middle East autocracies have refused to change their ways because they were protected by the wealth of their petroleum reserves. A nuclear Iran alters the regional dynamic significantly, and provides some leverage for us to demand reforms.
Second, becoming the primary provider of regional security in a nuclear Middle East would give the United States a way to break the OPEC cartel. Forcing an end to the sorts of monopolistic practices that are illegal in the United States would be the price of that nuclear shield, bringing oil prices down significantly and saving billions of dollars a year at the pump. Or, at a minimum, President Obama could trade security for increased production and a lowering of global petroleum prices.
Third, Israel has made clear that it feels threatened by Iran’s nuclear program. The Palestinians also have a reason for concern, because a nuclear strike against Israel would devastate them as well. This shared danger might serve as a catalyst for reconciliation between the two parties, leading to the peace agreement that has eluded the last five presidents. Paradoxically, any final agreement between Israelis and Palestinians would go a long way to undercutting Tehran’s animosity toward Israel, and would ease longstanding tensions in the region.
Fourth, a growth in exports of weapons systems, training, and advice to our Middle Eastern allies would not only strengthen our current partnership efforts but give the American defense industry a needed shot in the arm.
With the likelihood of austere Pentagon budgets in the coming years, Boeing has been making noise about shifting out of the defense industry, which would mean lost American jobs and would also put us in a difficult position should we be threatened by a rising military power like China. A nuclear Iran could forestall such a catastrophe.
Last, the United States would be able to stem the flow of dollars to autocratic regimes in the region. It would accomplish this not only by driving down the price of oil and increasing arms exports, but by requiring the beneficiaries of American security to bear a real share of its cost. And in the long run, a victory in the war on terrorism would save taxpayers the tens of billions of dollars a year now spent on overseas counterinsurgency operations.
What about the downside: that an unstable, anti-American regime would be able to start a nuclear war? Actually, that’s less of a risk than most people think. Unless the supreme leader, Ayatollah Ali Khameini, and his Guardian Council chart a course that no other nuclear power has ever taken, Iran should become more responsible once it acquires nuclear weapons, rather than less. The fifty-year standoff between the Soviet Union and the United States was called the Cold War, thanks to the deterrent effect of nuclear weapons.
There is reason to believe that the initial shock of a nuclear Iran would soon be followed a new regional dynamic strikingly like that of cold-war Europe. Saudi Arabia and Iraq would be united, along with their smaller neighbors, by their fear of Iran; the United States would take the lead in creating a stable regional security environment. In addition, our reluctant European allies, and possibly even China and Russia, would have a much harder time justifying sales of goods and technology to Tehran, further isolating the Islamic Republic.
Iran may think its enrichment plans will put fear into the hearts of Americans. In fact, it should give us hopes of a renaissance of American influence in the Middle East.