What Is Marissa Mayer Actually Doing? - Derek Thompson - The Atlantic

From a stark Yahoo! snapshot

"The upshot is that Yahoo, an original tech hero of the 1990s, has become a singular metaphor for the promise and woes of the industry: So many readers, so little lucre. Facebook and Google together make up nearly 70 percent of the mobile advertising market, with Mayer's company coming in at a distant third. Yahoo has room to grow, and money to spend, but, crucially, it doesn't have a dominant mobile operating system or a universal social network around which it can build an ecosystem for capturing and (ugh, yes, this word ...) monetizing mobile audiences. Google makes the software that powers 50 percent of all smartphones. Facebook has an ingenious one-column-scroll home built perfectly to incorporate native advertising seen by hundreds of millions of people a day. Yahoo has lots of popular sites and apps, but it doesn't have a strategic advantage in systems, search, or social.
Turning around Yahoo's image was hard work. Marissa Mayer did it. Turning around the business will be harder. "

What Is Marissa Mayer Actually Doing? - Derek Thompson - The Atlantic