By Cromulent Labs, developer of the Launcher app that Apple initially approved, then rejected for misuse of Notification Center. Emphasis mine:

During [a conversation with someone at App Review], I also asked specifically why Launcher was removed from the App Store after 9 days when other similar apps are still available weeks later. The answer to this question was the most interesting and informative response I had ever heard from them. They basically said that Launcher was a trailblazer in uncharted territories and that they felt that they needed to make an example of it in order to get the word out to developers that its functionality is not acceptable without them having to publish new specific guidelines. And they said that the fact that they aren’t seeing hundreds of similar apps submitted every day is proof to them that taking down Launcher was successful in this regard.

This was a pretty big revelation to me. After Launcher was rejected and the press picked up on it and started writing articles which painted Apple in a bad light, I was afraid that Apple might be mad at me. But it turns out that was actually the outcome they were looking for all along. They acted swiftly and made me the sacrificial lamb. And after that, removing other apps with similar functionality became a low priority for them.