Yammer
Used by 5 peopleyammer.com ↗

“We have our own social network in the form of Yammer, which is like a closed Facebook for businesses.”
Logan Cunningham Interview, Actor, voice actor (Bastion) · via Uses This 

“One app I have open all the time but I can't stand is Yammer.”
MG Siegler Interview, Tech reporter (TechCrunch) · via Uses This