Microsoft's social networking capabilities are perceived as weak—and the aim of its recent $1.2 billion purchase of enterprise social networking firm Yammer is to put this right. But what may also lie behind the acquisition is Microsoft's desire to get its hands on Yammer's expertise with the "freemium" software model and the viral, member-get-member way of attracting new customers.

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When Microsoft announced the deal at the end of June, Kurt Delbene, president of Microsoft's Office division, said that the plan is for Yammer to receive investment from Microsoft, but to continue to exist as a separate company. Yammer social networking will also be integrated (or continue to be integrated) with Microsoft's products. "Over time, you'll see more connections to your investments in SharePoint, Office 365, Dynamics, Skype and other cloud services," Delbene promised. He hinted that Yammer may be integrated with Exchange and Lync as well.

There's a good reason to keep Yammer separate: If it disappears into Microsoft's maw then there's a risk that it will never be seen again. "Microsoft has learned from what happened with its acquisitions of companies like Danger, Aquantive and Massive," says , an analyst at . (Microsoft announced in July that it has written down the value Aquantive, which it acquired for $6.3 billion in 2007, by $6.2 billion.)

In purely financial terms, Microsoft CEO Steve Ballmer says he believes Microsoft will benefit from owning the standalone Yammer. "As long as we continue to drive hard with Yammer as a consumer offering, and then we ramp up the Microsoft sales force to help rapidly accelerate the degree to which we get corporate conversions, I think we'll see a very, very nice revenue ramp fairly quickly," he said.