...The reason plots against Saudi oil installations are of such concern is the possibility that a catastrophic attack on a key facility could have a devastating effect on the world economy. Former CIA case officer Robert Baer famously wrote in his 2003 book Sleeping with the Devil:

A single jumbo jet with a suicide bomber at the controls, hijacked during takeoff from Dubai and crashed into the heart of Ras Tanura, would be enough to bring the world's oil-addicted economies to their knees, America's along with them. Indeed, such an attack would be more economically damaging than a dirty nuclear bomb set off in midtown Manhattan or across from the White House in Lafayette Square.

It is unclear if the present plot was intended to be catastrophic or merely disruptive. The tactics and weaponry involved (suicide bombers, explosive belts) are more suggestive of a disruptive attack. But that should not distract from the fact that these arrests are a reminder of the oil supply's vulnerability.