There was a time when emerging markets put the froth into Diageo numbers. Not so much any more. Over the past year, the maker of Guinness—and Johnnie Walker Scotch whisky, Smirnoff vodka and many others—has been wrestling with a host of issues in those markets. Now it's posted weaker-than-expected earnings, hurt by a slowdown in China and volatility elsewhere, with net sales down nine percent. In China, sales are down 20 percent.