Share |this page, you can see that Google knows who you talk to, what you talk about, how often and what social group they belong to in relation to you. Content that is shared between friends is recorded. If you click on say a Picasa photo album, Google tracks whose album it is and how you got there, maybe via someone else's Twitter or Myspace.
This seems to tie in with Google's well-crafted highly orchestrated master plan for social networking. This past week, they acquired Slide Inc who develops applications and virtual goods for Facebook, Myspace, and other sites.
To me, this feels like a stalker that is really open and honest about stalking you for your benefit. Your friendly neighborhood stalker man.