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Instagram apologized to its users today, saying it will "remove" language from its legal terms that would have let it sell users' photos or use them in advertisements.

In a blog post this afternoon, Chief Executive Kevin Systrom said it's "our mistake that this language is confusing" and that the company is "working on updated language."

"Since making these changes, we've heard loud and clear that many users are confused and upset about what the changes mean," he wrote.

Instagram's terms of use agreement announced yesterday sparked a user revolt unprecedented in its history -- and prompted competitors to tout their own services as more user-protective. It came three months after Facebook completed its acquisition of the popular photo-sharing service, which has over 100 million users, and follows recent efforts by the social network to increase revenue.

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No other photo-sharing service appears to have had a policy as broad as Instagram's now-abandoned language, which claimed the perpetual right to license users' photos to companies or any other organization, including for advertising purposes, which would effectively transform the Web site into the world's largest stock photo agency. A hotel in Hawaii, for instance, could have written a check to Instagram to license photos taken at its resort and then use them for its own purposes.

Google's policy, by contrast, does not permit the company to sell photographs uploaded through Picasa or Google+. Its policy says: "The rights you grant in this license are for the limited purpose of operating, promoting, and improving our services." Google now owns Instagram competitor Snapseed.

A Google spokesman told CNET this afternoon that Google+ and its other services protect their users' rights: "As our terms of service make clear, 'what belongs to you stays yours.' You own your files and control their sharing, plain and simple. Some of our services allow you to submit content. You retain ownership of any intellectual property rights that you hold in that content. In addition, on Google+ you can export your photos and other data whenever you'd like."

In 2007, Yahoo had a photo-rights flap of its own when its "brand portal" for the Nintendo Wii used Flickr images without permission, but it backed down soon after. Now Yahoo's policies for Flickr are photographer-friendly, saying the company can use the images "solely for the purpose for which such content was submitted or made available."

Another pitfall of the now-abandoned policy: If Instagram users continued to upload photos after January 16, 2013, and subsequently deleted their account afterward, they may have granted Facebook an irrevocable right to sell those images in perpetuity. There's no obvious language that says deleting an account terminates Facebook's rights, said Kurt Opsahl, a senior staff attorney at the Electronic Frontier Foundation.

In his blog post, Systrom emphasized that Instagram does not want to own users' photos, and that when users set their photos to private, they won't be made public under these new terms. He wrote that advertising is one of the many ways the company can sustain itself, saying:

We envision a future where both users and brands alike may promote their photos & accounts to increase engagement and to build a more meaningful following. Let's say a business wanted to promote their account to gain more followers and Instagram was able to feature them in some way. In order to help make a more relevant and useful promotion, it would be helpful to see which of the people you follow also follow this business. In this way, some of the data you produce -- like the actions you take (eg, following the account) and your profile photo -- might show up if you are following this business.

That sounds like a form of advertising similar to Facebook's sponsored stories ads. Facebook's sponsored ads are based on what users' friends "Like" on the social network. Once you like a brand's Page, your friends will see that like in their feeds.

Systrom's blog post comes after a day of silence from the photo-sharing network, which didn't answer questions from CNET, other media organizations, and users for over 24 hours.