The cargo is worth $100 million, so the ransom demand will huge. Although awash with money, this will annoy the Saudis, and interfering with the free flow of gasoline will anger the US.
The problem is, besides the people on the tanker, there are over 200 hostages already in Somalia waiting for their ransoms to be paid. Any military action against the Sirius Star could put them in peril. So in the short term, paying the ramson might be the safest option.
Predictably, it is all George Bush's fault...
"Two years ago piracy in the Horn of Africa was almost stamped out. The Islamists who took over Mogadishu and parts of Somalia in 2006 defeated several militias involved in piracy and warned others that they'd face punishment under a harsh version of Sharia. This tactic worked: "During the summer of 2006 there were no attacks [on ships] at all," says Pottengal Mukundan, director of the IMB.
But the Bush administration - which had tried to block the Islamists' rise by supporting a rival warlord faction - suspected Somalia's new leaders of sheltering Qaeda operatives. So Washington backed neighboring Ethiopia when it invaded in December 2006. The Ethiopians ousted the Islamists in short order and installed a U.N.-backed transitional government. But this only plunged Somalia into anarchy once more."
http://www.newsweek.com/id/154930