Google explains, “If there’s relevant web content written by people in your social circle, it will automatically show up at the bottom of your search results under a section called ’Results from people in your social circle.’” Your social circle is defined as "Gmail chat buddies, your Gmail contacts friends, family and co-worker groups, and people you’re publicly connected to on other social sites (such as Twitter and FriendFeed)" A connection to a site like Friendfeed can be done via your Google Profile, so as a side-effect, social search might make that profile a more important location to maintain for users. Full Article at Blogoscoped