The US Naval Institute once again tackles the threat from "swarming", essentially network-centric warfare upon the high seas (FP Online has more). The idea gained popularity in the wake of the Millennium Challenge 2002 wargames, when retired Lt. Gen. Paul Van Riper "decimated" the US Navy (see Adam Elkus' Red Team Journal for much more on the subject here and here).
In 2002, Gen. Van Riper was charged with playing the "Red" force--the enemy in a training exercise--in a computer simulation. The US--the "Blue" force--would be invading a "fictional" country in the Middle East *cough*Iraq*cough*. Van Riper sought to exploit the weaknesses in the US military's doctrine and equipment. Among Van Riper's bag of tricks was an anti-shipping force comprised of small boats, civilian aircraft, and portable anti-ship missiles (such as the Chinese-made C802, which struck the Israeli warship INS Hanit). Although taking massive casualties and using suicide attacks, the "Red" Navy was able to sink a large portion of the US fleet. The US military, presumably upset with the outcome, "re-floated" the fleet and continued with the exercise.
Fast-forward to the present-day. Iran is purchasing several speedboats, and already possesses anti-ship missiles like the C802 (it was assumed that the C802 that struck the Hanit was supplied by Iran). Could a navy such as this pose a threat?
"Springbored" at the US Naval Institute seems to think not. He notes that modern-day helicopters can make quick work of a speedboat attack--witness the success of the US Army's OH-58D Kiowa Warrior during Operation Prime Chance.
Still, it's worth mentioning that the success of the Hezbollah attack against the INS Hanit was a result of gross complacency on the part of the Israeli Navy. The crew ignored warnings of Hezbollah anti-ship missiles, turned the ship's defensive systems off, and lowered their guard as they ate dinner that evening. Perhaps Iran could capitalize on complacency by hiding ships among merchant traffic, and attacking during poor weather--when helicopters would be unlikely to take off or land.
It's certainly a dangerous option, and the US Navy would do well to take measures to prevent such an attack.
Ed. Note: I deleted a portion of this blog entry where I misinterpreted Sprinbored's post. I pray he doesn't track me down with a C802 :)