British Petroleum is taking a beating on Wall Street over the Gulf oil spill. But the economy is feeling the effects too. BP’s share value is sliding as though it was greased by, oh, loose oil or something. And it is taking the industry down with it. Oil company stocks were tumbling as BP continued to see its value head south. The company’s shares have lost 15% of their value since the spill began and the cumulative costs of the spill are now approaching a billion dollars. Ironically, the price of oil has fallen as well, though for how long,...