Video: HipChat vs Yammer

Group chat and video chat built for teams. Share ideas, code, and files with your team in real time. Rooms are perfect for individual projects, teams, or entire departments. You can also hop into a 1-to-1 chat with a coworker anytime. Connect your team and build genuine consensus with face-to-face video chat and real-time screen sharing. The next best thing to right next to you. HipChat free open-source (self-hosted) alternatives are: Mattermost, Rocket.Chat, Zulip
Yammer is revolutionizing internal corporate communications by bringing together all of a company’s employees inside a private and secure enterprise social network. Although Yammer is as easy to use as alternative consumer products like Facebook or Twitter, it is enterprise-class software built from the ground up to drive business objectives.
Face to face in the news:

2014 - Atlassian removes user limits in free HipChat version to compete with Yammer

Atlassian removed user number restrictions from the free version of its group chat for teams HipChat. Until now, the free version supported only up to 5 users. Thus, the only paid services in HipChat are video calls, unlimited search and larger file storage size. Obviously, such a kind gesture by Atlassian was caused by the increased competition from other representative of this segment - Slack. Slask launched last year and initially had no restrictions on the number of users and therefore, very quickly gained a lot of fans. Recall, HipChat - is a group chat widely used by software and internet companies. It allows you to create workspaces for different projects or departments and communicate in real time, share files, track the project progress.