Boing Boing reviewed the new book by Greg Conti titled, "Googling Security: How Much Does Google Know About You?" You can remove the question mark, since Google knows a lot about you, and probably far more than you realize:
"Conti enumerates all of Google's (often fantastic) services, describes how compelling they are, and then notes what information you disclose when you use them -- even when you only use them inadvertently (say, when you send email to someone with a Gmail account, or when you load a bookmarked Gmap that's been sent to a group of logged-in Google users, thus tying yourself to those users as part of the same group)."
The review was favorable:
"Conti's explanations are extremely accessible, even when discussing difficult and counter-intuitive subjects like cross-site scripting and cookies. Likewise accessible are his concrete recommendations for staunching the flow of personal information from your computer into Google's records. Finally, Conti does a great job of explaining why people who "have nothing to hide" might still want to keep their information to themselves... I've given the subject of privacy and Internet use a lot of thought, but even so, Conti's book opened my eyes to potential risks I'd never considered.
Put this book on your holiday gift list. It's on mine.