Developers Scott Sykora and Eugene Kaneko were sent a notice from Apple that their app would not be accepted into the App Store because it used the same "pinch to expand" peek gesture that Apple's own Photos app uses.
The app in question, Web Albums HD, is an iPad application that serves as a front-end for Picasa Web Albums from Google. When browsing through different albums, the pinch to expand gesture allows users to "peek" at what the album contains. First shown by Apple in their January iPad announcement event, developers Sykora and Kaneko found it a useful addition and worked to implement it into their own app. Because Apple didn't provide a way to implement the gesture in their SDK, Sykora and Kaneko coded the interface and gesture themselves. No undocumented or private APIs were used and all App Store procedures were followed.
When first submitted to Apple for approval, they received an email stating that the pinch to expand gesture for peeking is "associated solely with Apple applications" and that it would not be accepted unless removed. Sykora and Kaneko eventually ended up removing the feature and resubmitting it to Apple, which they then accepted.
"We removed the pinch expand, leaving just the tap to expand. We were approved but ended up having an inferior product."