In one of the worst kept secrets of 2012, Microsoft has announced today that it will be acquiring Yammer for $1.2 billion.  Yammer, a social enterprise software startup, is to become part of the Microsoft Office Division although Yammer employees will continue to report to CEO David Sacks.  Yammer will maintain its own path of developing its own products and services while “Microsoft pushes ahead to nudge further adoption alongside Sharepoint Office 365, Microsoft Dynamics and Skype.”

In the statement released by Microsoft, they write, “The acquisition of Yammer adds best-in-class enterprise social networking to Microsoft’s growing portfolio of complementary cloud services; world-class talent that knows how to deliver rapid innovation in the cloud; and a unique adoption model that appeals directly to end users,” cementing Microsoft’s status as still relevant.

Microsoft, through Yammer, has now brought to its portfolio the “core function in the architecture of modern, mission critical application,” that social enterprise encompasses.  Prior to the announcement Microsoft was was sorely lagging in activity steam development.  Twitter and Facebook have quickly brought to the forefront the importance of the activity steam which users have shaped to be an important part of their daily lives.  Yammer recently expanded its Activity Stream API “to support access control so the connectors won’t show users any record that they don’t have access to,” and also can be used to offer a more comprehensive alternative to “existing enterprise search products because users can use it to search for content across multiple cloud applications from a single search bar.”

Yammer, which recently announced a slew of new features including universal search, had “been working to build integrations with other business applications such as SAP, Netsuite, Salesforce.com and Microsoft SharePoint,” through partnerships culminating in today’s announcement of the move by Microsoft to acquire.  With this move, Microsoft sets itself up into a position to once again move slowly towards being a leader of social enterprise 2.0.

But as our editor-in-chief Mark “Rizzn” Hopkins points out in a Google+ post, there’s no clear path of intent for Microsoft’s latest buy.  As the space heats up and acquisitions become trendy–just look at SAP’s acquisition of SuccessFactors and Oracle’s acquisition of Collective Intelligence–it’s not entirely surprising that the Redmond-based software company wanted a social enterprise solution all its own.  But if you ask Hopkins, Yammer hasn’t proven itself an entirely worthwhile buy.  Unless Microsoft has something up their sleeves, the Yammer acquisition isn’t a justifiable one.