As Yahoo’s core business continues to sink, what’s Marissa Mayer doing at Walmart?

The weak Q3 earnings report from Yahoo has us wondering, again, about Yahoo CEO Marissa Mayer’s role on the Walmart Board of Directors. While Walmart purportedly brought Mayer on to help boost the retailer’s eCommerce performance, it’s clear that she has her hands full just trying to keep Yahoo afloat.

We always depend on Kara Swisher of AllThingsD to provide a peek behind the curtain of hype that surrounds all things having to do with Marissa Mayer. And Swisher doesn’t disappoint with her scathing posts on Yahoo’s Q3 earnings report.

In a (hilarious) post aptly titled “MarissaTV, the Yahoo Q3 News — If It Bleeds, It Definitely Does Not Lead”, Swisher points to the gap between Mayer’s ebullient presentation and Yahoo’s bottom line numbers, which reflect declining earnings and revenues, despite industry-wide gains.

… Mayer has the unenviable task of explaining why Yahoo’s earnings and revenue have declined in the quarter, even as the entire industry rises strongly. Of course, Mayer takes up the task with gusto. From the start, the results have been pushed aside for an enthusiastic list of all the good things going on at Yahoo.

Unlike many of the star-struck Marissa Mayer fans covering Yahoo, Swisher reminds her readers that it’s not Mayer’s business acumen but rather Yahoo’s stake in the Chinese eCommerce giant Alibaba that has been lifting Yahoo’s stock of late, despite the continued weak performance of Yahoo’s core advertising business.

As Swisher points out, half of Yahoo’s market value can be attributed to its stake in Alibaba, purchased years before Mayer joined the company. That stake is the “gold mine” which Mayer has tapped to fund a massive acquisition spree at Yahoo and to entice shareholders to hold on to their stock. Now that Yahoo has worked out a deal that will allow it to hang on to a larger-than-expected stake in Alibaba when the company goes public sometime next year, Mayer will have still more breathing room.

None of that, however, changes the fundamentals at Yahoo, and Mayer has yet to prove that she has the capacity to reverse Yahoo’s downward trajectory.  On that score, again, Swisher points to Yahoo’s disappointing results and also to Mayer’s refusal to provide numbers for key metrics, such as Yahoo’s mobile revenue percentage – despite her emphasis on the centrality of mobile to Yahoo’s future prospects.

So what’s the bottom line for Walmart watchers? Of course, Mayer joined Walmart’s board just prior to taking the top job at Yahoo. But, even if we assume that Mayer has highly valuable industry insight and connections to offer the company, it’s hard to imagine that Walmart’s problems are all that high on her list of priorities these days. So we have to wonder if Walmart execs and the rest of the Walmart board are regretting their choice? Or, given Walmart’s continued image problems, are they just happy to bask in the reflected glory of Mayer’s public relations machine for as long as they can?

What do you think?