Ackerman explains:

[I]n a sense, [US Admiral Jonathan Greenert] should hope Iran tries to close the Strait of Hormuz. There are few mistakes Iran could make that would be worse for it in the long run. Why? Because Iran would suddenly be responsible for sending world energy prices skyrocketing — perhaps to $200 a barrel — after a disruption of Gulf oil shipping. Washington usually has a hard sell when convincing other countries that Iran’s regional bellicosity and lack of transparency on its nuclear program merits a tough response. But when Iran hits the entire world in the wallet, the argument gets substantially easier.

Afshon Ostovar also thinks military escalation would be bad for Iran:

Iran's ability to keep the strait closed or constricted would likely be short lived. Because of the military operations that would be involved, and the damage it would do to the economies of the region, closing the strait would likely be considered an act of war against the United States and its Gulf allies. U.S. retaliation against Iran would thus be a near certainty, putting at risk much of Iran's maritime and littoral military assets. The United States could end up destroying much of Iran's navy, air force, and land based artillery just to clear the way for re-opening the strait. The United States might also take the opportunity to target Iran's nuclear sites, if not move to topple the Iranian regime altogether. Regional opinion (especially that of the United States' Arab allies) will most likely support military operations in such a context, and the international community will be hard-pressed not to support military action against an Iran that is willing to jeopardize world petroleum and gas markets for its own political purposes.

Remember Obama's supreme skill? Getting his enemies to self-destruct.