You have to decide to create a Google Profile and manually add these details in for Google to be able to build your "social graph." Doing so, , also authorizes Google to associate that info with your name within other users' social searches.

"Once you've created a Google Profile and added links to your various online social services, you've signaled a very clear choice that you're comfortable with the world knowing that information, including that you're a part of the other social networks you listed," Cutts explains. "Based on this opt-in decision, Google can start building a broader social graph."

In addition to your Google Profile connections, Google Social Search uses data shared by your Google Chat buddies and within your Google Reader account to build its results. It'll also branch out further, pulling publicly shared social data from friends of friends -- say, someone whom your Twitter buddy is following but you aren't -- then including that data within your Social Search results.

All of the indexed content is publicly shared, and you always have the option of removing any services from your own Google Profile.

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