Internal How NOT to use Yammer: Ragan offers prime example Is Yammer an efficient tool for employee communications—or another way to waste time? By Mark Ragan@MarkRaganCEODec. 23, 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.