Google does offer a page explaining how to disable their customization, but naturally they make it cumbersome since the practice maximizes the effectiveness and price of their ads.
While the reality that numerous commercial and probably other entities track our activity on the net has awful implications for our privacy, I get almost equally concerned that the net's ability to give us what we want locks us away in little information niches of our own making. Google searches aren't, easily anyway, going to lead us to sites and people that challenge our prejudices.
One small example -- I'm not interested in getting my sexual kicks from the web, so I NEVER see anything that suggests that the web is largest pornography mart in the world. But it is.
More seriously, as I range about the net, I also very seldom see the festering swamps of hate and bigotry that many of my fellow citizens inhabit. And consequently, I'm inadequately aware of much that is going on around me.
With that in mind, I share this exchange that I ran across on a Yahoo forum by chance the other day.
I admit to being shocked at the casual smugness of the racism, though I shouldn't be. It doesn't do us any good not to know.