"I hope that's not a sign of more restrictions to come on free accounts. For early-stage startups, I hope Yammer does continue to keep its many free features, which are beneficial until we decide to upgrade. If the acquisition means removal of the free option entirely, we may consider moving to other tools," she said via e-mail.

At the Graziadio School of Business, which pays for the software, Yammer is used by between 2,500 to 3,000 people, mostly students, but also faculty and alumni.

It uses Yammer for student communication, alumni community building and teaching, and it's especially effective for connecting users in different locations. The school has five campuses in Southern California and one in Northern California, as well as non-traditional students, such as working executives, who don't often attend classes in person.

The school uses a variety of collaboration tools, including Microsoft software, but Gautsch said "Yammer is the glue."

The IDG News Service