When you enter a search in Google do you expect to see the same results that another person would when entering the same terms? Don't count on it! Now Google's default search is "Personalized Search," a feature that used to be enabled only for those who signed in. Now Google uses a cookie to estimate how much you liked a particular site and rank search results differently based on that.
Google says "You'll know when we customize results because a 'View customizations' link will appear on the top right of the search results page. Clicking the link will let you see how we've customized your results and also let you turn off this type of customization."