I just posted a short article on the leaders in Social Networking by Gartner over on my Portal blog. Microsoft made the leadership quadrant because of it’s breadth of functionality, Yammer’s ease of use, a great vision, and a tremendous user base that shows no signs of slowing growth.
One of the strengths noted is that Yammer especially is becoming a social layers across the entire Microsoft platform like Office 365, Skype, Outlook/Exchange, etc. It’s obvious the cloud holds great potential for social, especially as users become accustomed to social having immediate impact.
I’m sure people like Rich Wood will focus more in depth on the Microsoft ranking but for more information on all vendors, see , my post or the Gartner report.