Social Media Instagram opens ads to third-party vendors; Twitter experiments with news Marketers can now purchase advertisements on the photo-sharing app; they could also benefit from a feature that tracks popular stories on the micro-blogging platform. By Beki Winchel@bekiwekiAug. 5, 2015 SHARE To read the full story, log in. Become a Ragan Insider member to read this article and all other archived content. Sign up today Already a member? Log in here. Learn more about Ragan Insider.