Starting in 2015, social networking sites must allow minors in California to delete their posts, according to a law signed by Gov. Jerry Brown earlier this week.

This seems like great news for teens, who don't have fully developed brains yet and may post things that they won't want future employers — or colleges — to see.

Darrell Steinberg, the state senator who proposed the bill, certainly thinks young people should be celebrating. "This is a groundbreaking protection for our kids who often act impetuously with postings of ill-advised pictures or messages before they think through the consequences," he said in a statement. "They deserve the right to remove this material that could haunt them for years to come."

In theory, this so-called eraser button will mean that impetuous posts will haunt teens no longer. It's a valiant goal, but as some politicians with embarrassing tweets could tell you, "delete" doesn't mean "disappear." (And can we note that those politicians are supposed to have fully developed brains by their ages?)

As the San Francisco Chronicle points out:

"If the underage drinking picture is posted by someone else, for example, it's not covered by the law. If the image is copied and posted to another Web site, that would not be covered, either.

"Web companies also are not required to scrub their servers clean of personal data, just remove the requested item from public viewing. ...

"There's an additional catch: the law doesn't extend to adults who want to go back and delete material they posted as minors."

Not only does this eraser button approach have some serious holes, but it also doesn't add much new to the state of social media privacy.

Facebook, Twitter, Instagram and several other social networking sites already give users the capability to delete posts. And they're accessible to everyone, in every location — not just minors in California.

One could argue that this legislation is a preventive measure, forbidding the sites to change their policies. But advocates for the law are acting like it's a breakthrough, not a safeguard.

Jim Steyer, CEO of the nonprofit Common Sense Media, in a public letter of support, mentioned the prevalence of Facebook and Twitter among teenagers, but he failed to mention that the teens already have delete capabilities.

When The Washington Post asked Steinberg about what makes the law different from current delete button options, he replied: "I think a lot of young people don't know — it's not always easily accessible to delete." The law says websites must provide minors with a notice that they may remove content and clear instructions on how to do so.

He also pointed out that the photo-sharing app Snapchat doesn't give users the option to delete photos. It will be interesting to see whether Snapchat changes its policy.

Another provision of the law, regarding online advertising, has more tangible changes: Sites that collect information from California minors will not be allowed to advertise certain products and services, including alcohol, guns, tobacco products, tattoos, drug paraphernalia or tanning beds.

Emily Siner is an intern on NPR's Digital News Desk.

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