Why might your face appear in Google ads, and how to stop it

You're considering buying a new pair of tube socks. A quick Google search pulls up some sock ads and below one of them you see your pal Kimberly's face next to a four-star review she's left for Sal's Sock Emporium. "Great deals on super soft socks, and so many fun colors!"

Google is betting that this type of personal recommendation from a friend will make people more likely to click on an ad.

Starting November 11, Google will be able to include Google+ users' faces, names and comments in ads. The content will be pulled from reviews they've made on Google+ or other tied-in Google services like YouTube or Google Play. The company updated its terms of service on Friday to include the new language allowing these "shared endorsements."

The adver-dorsements won't just appear on regular Google searches. Google ads are a sprawling business and a person's face could show up on any of the 2 million sites that are part of the Google ad network.

It's difficult to avoid Google+, the social network and user identity hub Google has been steadily grafting onto all of its popular services. Even if you don't think you have a Google+ profile, there's a good chance that one exists if you use the company's other services.

Google+ reviews are already used in many of the company's products. Look for a restaurant on Google Maps, for instance, and you'll see a star rating based on public reviews by Google+ users. Leave a review for an album you bought in the Google Play store and that is a usable Google+ endorsement.

If you don't want your face popping up in ads, it's easy to opt out. There is a settings page for Google+ accounts called Shared Endorsements. It explains exactly how the program works. Read through and if you're still uncomfortable with the idea, uncheck the box next to "Based upon my activity, Google may show my name and profile photo in shared endorsements that appear in ads."

You will still see familiar faces in ads, but your mug should no longer appear in other peoples' searches. If you hit +1 for a site, people in your network will still be able to see that you've liked it, which is not a new feature.

If you are really determined not to show up anywhere, just don't hit +1 or leave reviews on Google products or in the Google Play store.

Other social media companies have toyed with featuring their users' photos in ads. If you Like a company on Facebook or post a positive review on its page, that can be used in that company's Facebook ads.

You may have noticed a sponsored post in your News Feed that shows which of your friends have liked a particular brand. As with Google+ reviews, the key to not appearing in these types of ads is not endorsing brands. (Unlike Google, there's no opt-out option for sponsored stories on Facebook.)

The idea of promoting a brand and sharing positive opinions could appeal to many Google+ users who are already actively leaving reviews. Some people just really love brands, whether they're sports drinks, smartphone makers, movies or video games. They want to broadcast that love to the world, sharing their positive opinions wide and far.

Negative opinions can be equally useful information for their friends and families, but those bad reviews are not usable by advertisers. And for now, there's no -1 button on Google+ or Dislike button for Facebook.