Alibaba sneezes and Yahoo gets a cold. Or something like that. Alibaba delivered a weaker than expected earnings report, which sent Alibaba shares falling by 6.7% in pre-market trading. As a knock-on effect, Yahoo is tanking itself. It's down 5% in pre-market trading. Yahoo owns 15% of Alibaba, so it is pretty much just a tracking stock for Alibaba at this point.