Near Yammer's office, at the Caltrain station in San Francisco, people were reportedly heard talking about the possible buyout, according to Business Insider. Later, a woman named Sarah Taylor tweeted that she also eavesdropped on people talking about it at The Creamery, a coffee shop near Yammer's office.
That's not all, Business Insider reports that a source inside Yammer has also said that Microsoft is in the works of buying the startup.
San Francisco-based Yammer is sort of like: employees can post, share, and discuss items. It's become an integral tool for many startups, but it's also big among larger businesses. More than 80 percent of Fortune 500 companies use Yammer. If Microsoft buys Yammer, it could help the Web dinosaur modernize with social-enterprise tools.
Still this rumor is far from being confirmed. CNET contacted Microsoft and Yammer for comment and we'll update the story when we get more information.