Mat Honan at Gizmodo writing about The Case Against Google:
Google is a fundamentally different company than it has been in the past. Its culture and direction have changed radically in the past 18 months. It is trying to maneuver into position to operate in a post-pc, post-Web world, reacting to what it perceives as threats, and moving to where it thinks the puck will be.
This is precisely why Google joined the EULA and privacy policies of all its services, so it can track everything about you and serve you advertising for the benefit of Google's clients. Not your benefit, you're their product. You don't pay to use their services. Advertisers pay. They are Google's client.
It's not just Google though. The Internet is swarming with companies who's business models depend on tracking you. Many already know too much about you as it is. But Google is definitely the big one.
Mat Honan's article is worth a read if you're interested in this stuff. You should be.