For those who wish to frustrate the online profile builders, there’s a good extension now available‘
“The TrackMeNot Chrome extension takes a novel approach to protecting your privacy from search engines that can create profiles of you based on terms you search for. Rather than hiding your searches from them in some way, it takes the exact opposite tack: It inundates search engines with a blizzard of background searches from you, so that no practical profile can be built because there are too many random searches. It generates those search terms from a group of RSS feeds from sites including the New York Times, CNN, and others.
It also gives you a great deal of control over how you use it, including the search engines to which you want the searches sent, the number of searches done per hour, whether queries should be shown to you or remain visible, and so on.
It does this for the most popular search engines, including Google, Bing, AOL Search, Yahoo search, and Baidu (China's most popular search engine).” – Preston Gralla
From my point of view, it’s free, highly configurable, and doesn’t slow the browser at all.
You can download the Chrome extension here: https://chrome.google.com/webstore/detail/cgllkjmdafllcidaehjejjhpfkmanmka
It also exists for FireFox here: https://addons.mozilla.org/en-US/firefox/addon/trackmenot/