John Gruber, writing about the iPhone SDK:
Officially supported APIs take time to document…
You better believe it! Just ask the people in charge of documenting Launch Services (introduced in 10.0; documented in 10.3), Pasteboard Manager (introduced in 10.3; documented ten months later); Data Browser (introduced in 10.0; documented in 10.2); HITheme (introduced in 10.3; still not documented); and CoreAudio (introduced in 10.0; still not documented, as I don't count incomplete “preliminary” documentation).