Review: Samsung Nexus S
Though Google Android phones are known for being adept social networking devices, these features mostly rely on third party software, as the stock Android build offers no built-in social networking support. In fact, until you download official versions of the Twitter and Facebook apps, you can't even sync your contacts with your social circle. But those apps are free downloads from the App Market, and they keep getting better. Facebook now supports its own IM chat service, for instance. Twitter is still better on other platforms, especially iOS, where the interface is better and notifications come through much faster.
That said, Android does allow social apps to penetrate deep into the system. Once you have Facebook on board, you can sync your contacts, you can upload photos directly from the gallery, and you can start adding special widgets and folders to the homescreen panels, like a shortcut folder that gathers all your Facebook contacts who have phone numbers.
If you're a real social networking fiend, though, I would recommend a different Android, especially a Motorola Motoblur phone if you like to keep a constant eye on your update stream, or an HTC Sense phone if you want quick access to your friends' photo galleries and message history. Android is very flexible, but the Nexus S does not come with many social features out of the box, and even the third party widgets available from the app market fall short of the high quality software that HTC and Motorola are offering.