I have had a love hate relationship with Yammer. There are indeed both guidelines and governance in play. Most of the processes in place are concerned about ensuring client confidentiality and compliance rather than expected use. For internal comms Yammer was being used as another channel to reach employees, however how they used Yammer was and is still maturing. Initially it was used to republish content that was already available through the Intranet, however this has now changed to one where they are more active in engaging in dialogue and supporting leaders in getting their message out (for example helping to host Yammer sessions). It has been a powerful tool, and one thing that I think it does very well is to empower employees from across the organization to contribute content and though leadership. I think that internal comms roles will shift slightly as they begin to support and encourage content from within, rather than having to be the sole authors and creators of content.