Since Google announced that it will soon begin using photos and names of Google+ users in online ad campaigns, many of its account holders are discovering that they've already opted in to the feature unwittingly.

Under the new user terms and conditions that Google announced on Friday, the Internet search giant will be able to show the endorsement activity of Google+ users in its search result ads and "other promotional contexts."

As of Nov. 11, 2013, it says any user who has offered reviews of restaurants, products and stores could find those reviews showing up in ads displayed to their friends and connections.

These ads would appear on Google sites as well as on the more than two million sites in Google’s display ad network.

Google is calling the feature "shared endorsements" and says it will give users useful information to help them "find cool stuff", by showing them recommendations from people they already know.

Google claims it has 390 million active users per month on Google+, and that the name and photo that members already use on the social network will be the ones displayed in ads.

Google+ members have the option to keep their info out of ads, but many users are discovering they've already unwittingly opted in. The choice that users made about allowing "+1" endorsements is also the default setting for shared endorsements.

Want to opt out? Here's how.

On the Google+ home page, click on your name to get to your profile page. Then on the left-hand side, pull down to "Settings" to land on the "Account" page.

Then, look for "Shared Endorsements" and click on "Edit." There will be a statement there that reads: "Based upon my activity, Google may show my name and profile photo in shared endorsements that appear in ads."

This box is already checked for most Google+ users. If you do not want your profile information and comments used in ads, uncheck this box and then hit Save.

Google says it will not use the endorsements or recommendations of users who have reported being under 18 years of age in its ads.

It also says that changing the shared endorsement setting does not impact how your name and photo might look in shared endorsements that are not ads – for example, when users share a music recommendation displayed in the Play Store.

Facebook announced in August that it too would begin showing users' faces and names in ads about products they "Liked," even without the user’s explicit permission. Several privacy groups in the U.S. asked the U.S. Federal Trade Commission to begin an inquiry into the changes. Facebook eventually chose to suspend the ad plans.