In Google Talk, you can send or accept an invitation, but there's another option enabled by default: “Gmail automatically determines which contacts you'll be able to talk to without having to invite each other,” based on how frequently you mail each other. And since Gmail contacts include all the people you've ever replied to, you'll end up with a new Google Talk friend after replying 2-3 times to someone's messages.
A recently launched Google Friend Connect, lets you grow traffic by easily adding social features to your website. With just a few snippets of code, you get more people engaging more deeply with your site. a service that brings social features to ordinary web sites.
The invisible social network needed a way to expose information about its users, so you can now create a Google Profile. There's even a shortcut for accessing your profile: http://www.google.com/s2/profiles/me.
But without a place where you can share interesting stuff with your friends, Google Talk would be just a virtual social network. iGoogle, the site where you can aggregate all the things you find important, will become Google's main social site when the new version of iGoogle will be released. Among other features, the new iGoogle will add a Google Talk widget, support for OpenSocial applications and a gadget that shows updates from your friends.
Source:→ Google System