Here's what's happening: Exxon Mobil is trying to fend off the nationalization of a huge (i.e, multibillion dollar) oil project. The company is doing this by asking courts in the U.S., the UK and the Netherlands to sieze the assets of Venezuela's state oil company, Petroleos de Venezuela SA. As Chavez put it on a radio address yesterday: "If you end up freezing (Venezuelan assets) and it harms us, we're going to harm you. Do you know how? We aren't going to send oil to the United States. Take note, Mr. Bush, Mr. Danger. ... I speak to the U.S. empire, because that's the master: continue and you will see that we won't sent one drop of oil to the empire of the United States. The outlaws of Exxon Mobil will never again rob us."
This isn't the first time Chavez has said something like this, but I can't think of anyone who needs to buy gas that will enjoy hearing this threat, whether it's acted on or not.