Despite privacy concerns, Facebook (NASDAQ:FB) plans to send ads directly to phones via the new "Home" app.

Chief Operating Officer Sheryl Sandberg defended the practice, saying in interviews that mobile devices are effectively like TV. She calls it a "mass medium" that the social network hopes to monetize with more relevant pitches than we see in the average TV broadcast.

Facebook already tops Google (NASDAQ:GOOGL) as the leading supplier of mobile display ads, followed by Pandora (NYSE:P). But that may not last, says Tim Beyers of Motley Fool Rule Breakers and Motley Fool Supernova in the following interview with The Motley Fool's Erin Miller.

Research firm eMarketer predicts that Google will take the top spot come 2015. "Home" is Facebook's effort to stay ahead. A twin bet on both leaders is the most likely payoff for investors, Tim says.

Do you think Facebook can win in the war for mobile ad market share? Please watch this short video to get Tim's full take, and then leave a comment to let us know whether you'd buy, sell, or short Facebook stock now, and why.