Recent acquisition of Yammer by Microsoft has redefined the corporate social networks.
Nice Article by The Economist -
Bring your own network
“Social networks for companies mimic the methods of public ones, which lots of firms already use to push their wares and to listen to what people say about them. In forums that look like Twitter feeds or Facebook pages, sales teams can share leads and information about clients (some of it gleaned from profiles on public networks), ask for and get speedy approval of discounts and slap one another virtually on the back for clinching a deal. Groups can be formed for specific projects. Documents can be shared. Flows of work can be organised. Expertise can be sought and pooled.”
Read full article – http://www.economist.com/node/21557341