Google Social Search allows users to customize their search results with content generated by those in their online social circle. But it requires everybody in that social circle to opt-in into the program (Google Profile). Thus the members of the user’s social circle will have to actively add links to the content they produce through services like Blogger, Twitter, Facebook, to their Google Profiles in order for it to show up in the searches some in their social circle does for a given topic.
If you are interested in Google’s new service in detail I’d recommend you Tom Krazit’s post on CNet , the original post on Google’s Blog (a good read with pictures and videos), Matt McGee’s post on Searchengineland or a post on the issue in German by André Vatter.
What strikes me however is the fact that Google doesn’t actively search for your private data but instead places the burden on the individual user to actively produce content and to indicate to Google who is within his social circle. Thus a prerequisite for using Google Social Search is the use of Google Profile, a service I am heavily sceptical about.