Ever since Microsoft bought enterprise social-networking vendor Yammer two years ago for $1.2 billion, the Redmondians have allowed Yammer to continue to operate fairly independently.

But Microsoft management may be tightening its grasp a bit on the San Francisco-based Yammer business.

On July 24, Yammer Co-founder David Sacks announced on Twitter that he was leaving Microsoft and Yammer.

"Thank you to my current and former YamFamily for 6 great years and to Microsoft for the last two. I look forward to new adventures," Sacks tweeted.

Before founding and heading up Yammer as its CEO, Sacks was PayPal's Chief Operating Officer.

Microsoft has been integrating Yammer's enterprise social capabilties with a number of its own products, including Office 365 and SharePoint, since it bought the company. Microsoft has taken a few pages out of Yammer's playbook , in terms of how to more rapidly update and iterate on its technologies.

A year ago, Microsoft created a "Yammer North" team in Redmond to help the company coordinate with Yammer and bring some Microsoft processes and thinking, when appropriate, back to the Yammer team.

But now Microsoft is moving Yammer into the Office 365 and Outlook development teams, which are headed by Microsoft Corporate Vice President Rajesh Jha . A lead from Jha's team, Kristian Andaker, is going to move to San Francisco to head up the Yammer Engineering team there, I hear from my contacts.

I asked Microsoft officials what was happening with Yammer and was provided with the following statement:

"Yammer is an integral part of Office 365 and it is being used by more than 500,000 organizations to transform how they work every day. Since we acquired Yammer in 2012 we have been working together to bring the integrated benefits of enterprise social to all our Office 365 customers. As we’ve seen the Yammer experience extending throughout Office - giving people new ways to collaborate and work together – it’s now time to bring the Yammer organization together with our Outlook and Office 365 Shared teams as the next logical step in delivering an integrated set of social, collaboration, and communication experiences that enable companies to work like a network.

"We thank David for his commitment to Yammer and Microsoft and wish him the best in his future endeavors.Yammer has grown tremendously since the acquisition in 2012, and is now an integral part of Office 365 and used by more than 500,000 organizations. As part of our long term plan, David has played an instrumental role over the past two years in building a strong leadership team to set a solid direction for Yammer as part of Microsoft Office 365 and our vision for enterprise social."