With Messenger, users can communicate, bring data with them, invite their friends...
...and their friends invite their friends, and...(you get the idea - huge network!).

Messenger Blog
Have you ever wondered how well the Messenger Web Toolkit scales? What if we told you it scales enough for some of the largest web sites in the world? Well it does! Hotmail and MSN both depend on the Messenger Web Toolkit to offer instant messaging functionality to their users. Hotmail alone has more than 350 million active users worldwide. Hotmail (http://mail.live.com) Hotmail provides u....
We’ve been working hard on the Windows Live Messenger Web Toolkit (MWT) which allows you to connect your web site to 330M+ people who use Windows Live Messenger every month! Today we’d like to announce the availability of the Messenger Web Toolkit v3.5 which will enhance the user experience, make it easier to enable sharing via Messenger scenarios on your site (new sharing control), and enable n....