Yammer has experienced dramatic growth since launching in September 2008. The company now has more than 1.5 million verified corporate users, including employees at more than 80 percent of the Fortune 500.

The new funding will help the company capitalize on this momentum by rapidly scaling its operations. Yammer plans to triple the size of its engineering team and significantly grow its sales organization. In addition, with Yammer now in use in 136 countries, the company will open offices in Europe and Australia in response to global demand.

"The consumerization of the enterprise is happening in a big way and Yammer sits right in the middle of this major trend," said Mamoon Hamid, principal at U.S. Venture Partners. "Yammer's growth has been explosive and they've proven the value of the freemium model. The new infusion of capital will help the company scale to meet the considerable market demand."'

"Yammer has defined -- and is the fastest-growing company in -- the category of Enterprise Social Networking," said Yammer CEO David Sacks. "This financing recognizes our leadership and positions us to accelerate the execution of our ambitious product roadmap and global expansion plans."
New Executive Appointments

To help manage its growth, Yammer has added new executives to its management team:

• David Stewart has joined Yammer as vice president of product management. Previously, David served as senior director of product at Playdom, where he focused on virality and user acquisition across its social gaming applications (Playdom was recently acquired by The Walt Disney Company.) Before Playdom, he was the product marketing lead for YouTube's platforms and partnerships. Before that, David was the business marketing lead for Google's Commerce team, which included Google Analytics, Checkout, and Product Search. Prior to Google, he was a strategic consultant at the Boston Consulting Group. David holds a B.A. and M.B.A. from Yale University.

• Mark Woolway has joined Yammer as vice president of corporate affairs. Previously he was a managing director at Clarium Capital, a global/macro hedge fund. Before that, he was vice president of corporate development at PayPal, where he helped lead the company's successful IPO process. Mark also practiced corporate law at Munger, Tolles & Olson. He holds a B.A in Economics from the University of California, Berkeley, and a J.D. from the University of Chicago Law School.