Here’s why it’s legal for Google and Facebook to use your face in ads

Social advertising — using a person’s profile to market to others in their social networks — is catching on with more companies, but raises the question of how much legal control people have over their own image.

Google(s goog), for instance is going to plunk your photo into ads: when your friends and contacts do a Google search — or explore Google Play and YouTube — they could see your smiling face endorsing a product or service. The plan has touched off a protest and some grumbling from a US Senator, but should go forward in November. When it does, Google will have its own version of the “Sponsored Stories” that Facebook(s fb) has shown us for years.

But what if you don’t want to be in an ad: can the companies use your picture anyways? The short answer is yes. Here’s a quick Q&A on what Facebook and Google are up to and how they make it legal.

So how I do appear in product endorsements in the first place?

In the case of Facebook, when you “Like” a company or product, the social network takes that as an endorsement and offers it for sale. As for Google, that’s why the company keeps prodding you to sign up for a “profile” on Google+ — once you do, it will (soon) turn any of your reviews or likes into endorsements.

Can any company just take my picture and use it to endorse stuff?

No. Under American state privacy laws, there is a “right of publicity” that allows you to control public displays of your image. This applies to celebrities and famous athletes who want to protect their endorsement power, but it also extends to everyday people. Companies can’t put your face on a billboard — or in an internet ad — to sell things unless you give them permission.

So can I sue Facebook and Google if they put me in an ad?

The key word here is “permission.” You gave those companies permission when you signed up and agreed to their terms of service.

But this wasn’t part of the deal when I signed up!

The terms of service for Facebook, Google and other internet companies include a clause that give them the right to modify their terms from time to time. When you receive an “update,” that’s what is happening — the companies are letting you know the rules have changed and, if you don’t like it, you can quit.

It’s true that Facebook had to pay $20 million over Sponsored Stories — but that’s because they went ahead without updating their terms first.

But it’s not practical for me to just quit Google or Facebook — is there any other way to avoid appearing in the ads?

Google provides an out-opt mechanism (though it doesn’t apply to Google Play). You can’t opt out of the Facebook system.

The best option for now is to be judicious about what you “like” or “review” since these actions will likely be shown to your contacts on Google or Facebook. (Twitter may be next).

So I should just learn to live with being a product spokesperson?

Pretty much — that’s the price of admission to sites like Google and Facebook these days. The companies would argue that it’s a pretty good deal since their services are otherwise free and, in any case, you receive better, more relevant advertising. And they’re unlikely to give up “social ads” anytime soon since, as Facebook’s Sheryl Sandberg has disclosed in court documents, such ads are three times more likely to lead to a purchase.

You might counter that the companies could charge a subscription fee and then reduce the price in exchange for accepting ads — but that’s a question for another day.