The core of Mango's social networking features will be found in the People hub, which will include updates fed from Facebook, Twitter, and LinkedIn. So rather than heading to three individual apps, you'll be able to check them all from one location.
If you've got plenty of contacts, there's a reasonable chance that you'll be inundated with updates. So Mango will let you filter, and show updates from any one of those individual social networking sites, rather than all of them.
In addition, the Live tile on the Windows Phone 7 home screen will display any new activity on those social networks, such as whether someone has written on your Facebook wall, or mentioned you on Twitter. From this same location, you'll also be able to perform a variety of social networking tasks, such as replying to messages, retweeting messages, and so on.
For details, and to see it in action, check out the video from Microsoft, below.
It would be nice to be able to filter not just by service, but by users, searchwords, and so on. Still, what's built into Mango appears to be a very good app.
This is exactly the kind of thing that can help Microsoft sell Windows Phone 7 devices. Microsoft's ad campaign for the devices, while clever, takes the exactly wrong tack: It positions Windows Phone 7 as the operating system for those who want to spend less time with their smartphones. Instead, Microsoft should focus on all the nifty things Windows Phone 7 can do --- and its social networking features are exactly the kind of thing it should be highlighting.