energy sector

4:40 pm : The week's wild ride has concluded, but onlookers might not know it by the relatively mild close had on Friday. The S&P 500 surged almost 12% Monday, suffered its biggest drop since the 1987 crash on Wednesday, and rallied more than 4% Thursday. On Friday alone the index swung nearly 7% from low to high before finishing with a 0.6% loss.

Few things stir the blood more than Wall Street firms getting into a good old scrap. Put aside the internecine squabbling at Morgan Stanley - they don't come much better than the current dust-up between Citigroup (metals "super cycle") and Goldman Sachs (oil "super spike"), and Merrill Lynch - whose chief equity strategist, David Bowers, on Monday poured water on the idea of what he described as a resources bubble.