One good thing has come out of all the Somali pirate activities. It has given ship owners, and many navies and intelligence agencies, a better idea of what hostile parties can, and cannot, accomplish when trying to seize control of supertankers (ships over 200,000 DWT). The largest of these ships (about half a million DWT) can carry over three million barrels of oil. At a hundred dollars a barrel, that's a very valuable cargo. While the pirates seek a huge ransom for taking one of these ships, terrorists have other plans.
Osama bin Laden's recently captured files revealed that he was trying to organize the seizure of one or more supertankers, in order to strangle the world economy. Turns out that several intelligence agencies already believed that this was a major goal of al Qaeda. No details of how far bin Laden and his crew had gotten, but the efforts of the Somali pirates in grabbing these large ships has been studied carefully, and many supertankers now have more security measures and equipment installed.
The largest tanker ever taken by the Somali pirates, the 318,000 DWT Sirius Star in 2008, carried over two million barrels of oil. It had a crew of 25. A ship like this being stolen has been a nightmare scenario for those who fight terrorism. In theory, a large ship like this could be steered to the Straits of Malacca and sunk. This would disrupt the world economy, and create a sharp increase in shipping costs. There are other places where an inconvenient sinking could cause large, and long-term, economic disruption. Bin Laden was obsessed with carrying out these kinds of attacks.
But there are lots of known difficulties, and some more recent, purposely kept secret, ones. The known problems for the terrorists is that supertankers are easy to track. Not only do they carry multiple electronic devices, but their sheer size makes them easy to spot via satellite, reconnaissance aircraft, or using the sonar on nuclear subs. Second, these ships are actually very difficult to sink. Third, security on these large ships has changed in the last few years, since the Sirius Star was hijacked. And more changes are always in the works.