No surprises here, but on Tuesday evening Google launched its own social network, capitalising on its existing Gmail user base and expanding mobile presence.

Google Buzz is in the process of being activated on the Gmail accounts of the webmail service’s 170 million or so active users, giving the web giant an installed user base for Buzz.

A set of new features adds functionality like status updates, inline images and links, and location, where posts tagged with geographical information have an extra dimension of context based on the poster’s location.

The service integrates tightly with Google’s other services – Gmail, Picasa, Google Reader, and YouTube – and also hooks into the likes of Flickr and Twitter.

The aggregation layer seems to be a popular approach to social networking these days and Buzz sends responses to posts straight to the inbox, adding new comments in real time. The contacts a user emails most from Gmail are automatically ‘followed’ so users don’t have to start building a new friends list from scratch. Google said that Buzz also recommends posts from people you’re not directly following, such as ones your friends are having a lively conversation with.

On mobile, Buzz adds a new layer to Google Maps, which allows you to see Buzz comments and updates near you or anywhere on the map, so in addition to checking out updates from people you’re following, you can also see info from the people around you.

Buzz for mobile is already available for the iPhone and Android but the kicker is that the app is only working on Android 2.0 at present, while the layer for Google Maps is only backwards compatible as far as Android 1.6.

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