Yammer, Inc., the leading provider of enterprise social networks, has announced it has received $17 million in its fourth round of funding, bringing its total financing to $57 million. The Social+Capital Partnership, a new fund established by former Facebook Vice President Chamath Palihapitiya, led the round with previous investors Charles River Ventures, Emergence Capital and U.S. Venture Partners also participating. Palihapitiya will have an observer's seat on Yammer's board of directors.

Yammer has grown at a rapid pace. It has been adopted by over 100,000 businesses in 160 countries in less than three years, including employees at more than 80 percent of the Fortune 500. Major corporations such as 7-11, Ford, Southern Company, Shell and SuperValu have deployed Yammer this year, proof that enterprise social networking is entering the mainstream.

Yammer is expanding rapidly internationally to meet global demand for its product, and the additional funding will be used to scale operations across its offices in San Francisco, London and Melbourne. The company is actively hiring employees in sales, engineering and customer support.

Palihapitiya is not the only Facebook principal involved in Yammer. He joins Sean Parker, Facebook's founding president, who is on Yammer's Board of Directors, and Peter Thiel, who was the first investor in both Facebook and Yammer.