Yammer doesn't just make social networking ok at work, it makes it a must. Widely recognized as the original enterprise social network that increases collaboration amongst employees, Yammer was originally created simply as an internal collaboration tool by the folks at Geni – a company started by PayPal co-founder David Sacks and entrepreneur Adam Pisoni and then backed by long-time friend George Zachary of CRV. It did not take long for both company insiders and investors to see that this internal tool had potential way beyond the walls of Geni. Today Yammer is used by more than 100,000 companies to facilitate better problem-solving, brainstorming, and by connecting the right group of people for any given project, idea or opportunity. Yammer was acquired by Microsoft for $1.2 billion in July 2012.