Microsoft buys Yammer for $1.2 billion By msnbc.com news reports Microsoft (MSFT) agreed to buy online social network firm Yammer for $1.2 billion in cash, which will allow the software company to offer a service like Facebook's to corporate customers. Talk of a deal had circulated earlier this month, but the two companies only confirmed the deal on Monday. The acquisition represents Microsoft's latest attempt to adapt to a major shift in the technology industry, one that is fueling demand for more Internet services and social networking tools. That shift is threatening to weaken Microsoft's position as the world's largest software maker. Four-year-old Yammer, which has 5 million users of its private, in-company social networks, will become part of Microsoft's Office unit under Kurt DelBene but will still be led by current Chief Executive David Sacks. Yammer, which is based in San Francisco, had raised about $142 million since its inception four years ago. Last year, Microsoft bought Internet video chat service Skype for $8.5 billion in the biggest acquisition in the company's 37-year history. Yammer plans to continue offering a standalone service, while Microsoft will encourage its use alongside its other business products, including Office and SharePoint. "When we started Yammer four years ago, we set out to do something big," Yammer CEO David Sacks said. We had a vision for how social networking could change the way we work. Joining Microsoft will accelerate that vision and give us access to the technologies, expertise and resources we'll need to scale and innovate. Microsoft shares were down $1.01, or 3.3 percent, to $29.69 in afternoon trading Monday.