Analysis Microsoft has finally tied the knot with enterprise social networker Yammer, and in a press call following the announcement, Steve Ballmer laid out the future for Redmond’s newest recruit.

“Yammer will be a fundamental part of the Office family,” a “thrilled” Steve Ballmer said, adding that it would become a core addition of SharePoint and Lync services on the cloud. It brought a “very unique” set of skills, and Yammer will operate as a separate but equal section of Redmond’s Office team.

Yammer’s viral business model – spreading through a free social service for people in business and then upselling features into IT departments that want to run the platform – was a key part of the deal, Ballmer said. Microsoft hopes Yammer will be the goose that will continue to lay golden users; it’s clear that Ballmer & Co. want Yammer to continue to add customers even if they aren’t using Redmond’s software.