As oil prices slump, there are a number of sources that offer explanations of what might happen. The IMF has a good one, as does Chase.
Generally there is a concern that major oil source nations in the Middle East need expensive oil to ensure their budgets stay balanced. Failure to do this will eventually lead to a financial crisis, and as we have seen, all crises in the Middle East cast long shadows.
Actually, a number of key oil producing nations outside the Middle East are also in unsettled conditions; Venezuela, Nigeria and Angola come to mind. Of course oil consuming nations are pleased as lower oil prices are an economic stimulus.