Short story: GP Apps made iVidCam, a video recording app. Apple rejected it for using undocumented APIs. The developers appealed on the grounds that other camera-related apps also use undocumented APIs and demanded Apple allow it in, and let them sell it for 2 months before Apple released their own video recording functionality, as anticipated for WWDC 2009. Apple thanked them for pointing out other API violators, said they would investigate, and let the rejection stand.
Long story, including personal response from Apple VP of marketing, Phil Schiller: See GPApps.com.