Microsoft has announced that document previewing and editing in Yammer will be provided through Office Online.
First, the document preview and edit experience for files uploaded into Yammer are now powered by Office Online. When you click the Edit File link in Yammer, a new browser tab opens up with a full-screen view of the document. Make changes and comments directly in the document using Office Online. When you’re done, simply close the tab. Your changes are automatically saved in Yammer, where you have the ability to review the version history of each file and mark documents “Official.” In the near future, you’ll also be able to co-author documents in real-time and translate documents in Yammer into 30+ languages using the Bing Translator.