25 case studies of companies using Twitter to increase sales Pretty thorough list from marketer Kyle Lacy. This post includes case studies from Dell Outlet, Levi’s, the U.S. Geological Survey, and more. Take a look . By Ragan StaffJan. 25, 2011 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.