This seems to tie in, in a way, with the now-freed British captives.
From Stratfor (just before the British were let go):
“... The Iranians, like the Americans, also have found it necessary to demonstrate a lack of intimidation. And for Iran, capturing 15 British sailors and marines was an excellent device…
... The Iranians have shifted the spotlight away from Baghdad and to the southern region of Iraq—to the area dominated by Shia and held by the British. The capture of the British personnel coincided with some fighting in the Basra area among Shiite militias.

In this way, the Iranians have sent two signals.

The first was that while the United States is concentrating its forces in Baghdad and Anbar province, Iran remains perfectly capable of whipping up a crisis in the relatively quiet south—where U.S. troops are not present and where the British, who already have established a timeline for withdrawal, might not have sufficient force to contain a crisis. If the United States had to inject forces into the south at this point, they would have to come from other regions of Iraq or from the already strained reserve forces in the United States. The Iranians are indicating that they can create some serious political and military problems for the United States if Washington becomes aggressive.
The second is a statement about the negotiations over Iraq. While they are interested in reaching a comprehensive settlement over Iraq, the Iranians are prepared to contemplate another outcome, in which Iraq fragments into regional entities and the Iranians dominate the Shiite south…
... Where the United States has been trying to generate a sense of danger on the part of Iran with rumors of airstrikes, the Iranians have signaled that they aren’t worried about the airstrikes—and then raised the American bet by forcing the United States to consider what its options might be if all hell broke loose in southern Iraq. Tehran is saying that it has more credible options than Washington does.”

Interesting!

ESPECIALLY the Russians. They’ve already sold AA weapons to Iran and probably would not mind seeing yet another American foreign policy debacle that would result in higher oil prices. Why would we trust the Russians not to tell the Iranians, and why wouldn’t they?

It’s not like the Yeltsin years. The Russians don’t need us like they used to.

Iran is not an option, and the Iranians know it. Were the U.S. operating under a state of war, i.e., an officially declared war with all the powers that such implies, the Iranians might be more circumspect. But they can read the tea leaves and they know that this adminstration’s options are limited. Brilliant move on their part to grab the Brits, remind everyone that they have options, and then release them in a gesture that will win the hearts and minds of the perfected idiot class.