Like almost all of Iran's threats, I take it seriously but don't expect it to happen.

Think it through.

If Iran closed the straits.. Who stands to benefit?

China gets nearly 20% of it's oil from Iran. They'll be ticked off.
Saudi will not be able to make THEIR shipments. They'll be ticked off.
Iraq, no friend of Iran, won't be able to ship.
Same for Kuwait.

If they close the Strait, they'll have EVERY modernized military in the world with the possible exception of the Russians against them. Their ships will be destroyed, their oil sales will cease and the government will lose even MORE face.

In other words, if Ahmanutjob closes the Straits, he's signed his own death warrant.

We may not be good at nation building, but we sure can bomb the hell out of any ships or land installations that would try to shut down the Straits. And make no mistake, the Iranian clerics can bleat, moan and threaten all they want - nobody will care. Cut off the oil? You can bet people will care - and fast. You think China will stand idly by? The US? Iran's neighbors? I don't think so.

Don't get me wrong, it'll be ugly - but it won't last.