I've been trying to extricate myself from Google's All Seeing Gaze. (for more info on why, see this article linked by @brlamb).
There are plugins and opt-out cookies etc... but all of those work only in the browser. Often, in just a specific browser. I think I've found a better way. No opt-out. Works for any app that touches The Tubes.
Just modify your /etc/hosts file to include the contents of this great shared .hosts file. All requests for nefarious tracking servers will be dumped to 127.0.0.1 (your own computer) rather than routed out to The Big Snoops In The Ether. Some semblance of privacy, without having to opt out in every browser you use.
The sample file had ad.doubleclick.net commented out because it breaks sears.com and other sites who somehow route actual content through the ad tracking network. I say, if a site is that evilly designed, screw 'em. I've uncommented the line and am blocking all requests for known doubleclick servers.
Also, I switched my DNS away from the convenient and fast Google DNS servers. Sure, they're fast, but using their DNS servers means they're able to see everything I do online, no matter what app, no matter what protocol. No, thanks.
Finally, I've stopped using Google Quick Search Box. It'd probably be OK to just turn off the "send usage data to Google" and "suggest web pages..." settings, but I'm reverting to just using Spotlight instead. It's local. It doesn't report stuff to The Cloud.