Twitter is expanding its advertising products with retargeting capabilities for marketers to better reach audiences on mobile devices, the company announced today. It’s the next leap for the newly public company's still-nascent advertising business. Twitter will try to leverage its unique position as a highly trafficked network on both the mobile and desktop-based Web. The company counts more than 200 million active users, and about 75 percent of those users access the network from mobile devices. That’s a lot of data across devices—data coveted by advertisers and ad...