The app is called The XChange, and it's designed to help users connect with each other for sexual encounters. It's essentially a huge, automated chat room that lets users build simple profiles and upload pictures.
The option to upload pictures is what nudges the app into adult territory, because even though the app's self-documentation comes with the warning not to upload nude images, ever since its July 1 debut in the app store, users have been uploading thousands of nude images.
The app has already been removed from the App Store as of Friday afternoon, but Apple's initial approval of it drew criticism from the tech punditry.
"Why is Apple approving these apps in the first place, knowing they are going to pull them down later?" said analyst Jesus Diaz of Gizmodo, who also asked why Apple doesn't remove apps like Safari, which can access more adult content that any individual app.
"This is stupid and has to stop," he said. "Either you apply the same filter to everything, or you open the application market for real. Just make sure things work, and are not illegal on its own, not because of the potential content they may fetch from the Internet."