Yet last week, when Yahoo’s board met to review the planned January spinoff, it decided to call off the deal. On Wednesday, the board announced that Yahoo would pursue a spinoff of its core Internet business instead, leaving the Alibaba stock in the old company. Although Yahoo’s board said it still believed that the company would prevail in any tax dispute, too many people on Wall Street were worried that challenging Uncle Sam over a possible $10 billion tax bill was just too big a risk, and those fears were depressing Yahoo’s stock price.
See: http://www.nytimes.com/2015/12/10/technology/yahoo-alibaba-spinoff.html?_r=0