If you watch the moves of Google for some time, you can recognize without being too paranoid a consistent strategy of collecting as much data about people as possible.
It began with search queries, which are a very good indication of what an indiviuum is interested in. But bringing the people to sign-up and log-in personally to your search engine makes, overcomes the quite inaccurate IP- or cookie-based method to get distinct users and gives a direct relation between queries and actual people sitting in front of the computer. How do you achieve that? The answer is simple: Offer a free eMail address which tons of space so that you never have to throw away a mail ever again (Google Mail) or a customizable start page (iGoogle) and take that log-in to the search page. Voilá, really personal search.
But that all limits Google to its own pages, wouldn't it be much better to get data about people, even when they are not visiting Google servers? Easy solution to that as well: Offer an affordable ad system (Google Ads) that is working fast, is easy to implement and gives webmasters a quick way to earn some money. Or set up a free, really cool web statistics tool (Google Analytics), that is superior to everything that is out there. Doing so, extends the "span of collection" significantly.
Overall this already produces a huge amount of "coverage": All Google websites, websites that want to make some money and websites that want good statistics. But let's not stop there: What about the location of people, wouldn't that be interesting, too? No sooner said than done: Implement a maps serivces (Google Maps) and make it available on cell phones, which, by nature, can be used to determine the location of the user very exact (in contrast to IP-based locating mechanisms). All cell phones can use the cell phone towers to determine their location quite good already, but putting GPS chips in them make the result very astonishing.
Nowhere near enough, after having the people's interests (search queries), their contacts and conversations (mail), visited webistes (search queries, ads, stats), location (maps), they just added a new interesting tool: Voice search (Google Mobile App), which can be used to extract even more information, for example gender or mood. That's possible because in contrast to traditional voice recognition systems on phones the recognition itself is not done on the cellphone, the recordings are sent to google and are processed there. And after having collected enough audio fragements of one's voice, it should be no problem to create vocal fingerprints and use it to recognize or imitate people (at least when you believe some hollywood movies).
My remarks draw a picture, that is most likely exaggerated (though it covers only a few Google Services), but it should be helpful to generate some awareness about the piles of data Google is accumulating.