Apple has rejected a lot of apps in the past year of its existence and usually without giving the reason. The latest app we all heard about was the Google Voice app. Since then, Google brought the issues to the attention of the FCC to investigate.
The FCC asked Apple to answer quite a few questions and today Apple has finally answered. The list is lengthy and fairly comprehensive and claims to have not rejected the app from Google, but rather that they are still investigating it. The document is worth the read if you have the time and has been posted by APple in full on their site. Check it out [Here]