In  recent update to its Terms of Service, Google has announced a brand new strategy called “Shared Endorsements” by which it will show your face, +1 recommendations and reviews in advertisements. For example, When you search for a restaurant, you may see an ad including a 5-star review by another friend.
The good part is, you can opt-out from this services and keep your recommendation and reviews private.
Just head on to Google Settings page, scroll down and  un-check the check box that says “Based upon my activity, Google may show my name and profile photo in shared endorsements that appear in ads.”, that’s it
Here’s an excerpt of Shared Endorsement
“Feedback from people you know can save you time and improve results for you and your friends across all Google services, including Search, Maps, Play and in advertising. For example, your friends might see that you rated an album 4 stars on the band’s Google Play page. And the +1 you gave your favorite local bakery could be included in an ad that the bakery runs through Google. We call these recommendations shared endorsements.”
