This article is by far the most comprehensive answer to this excellent question:
app-store rejections
The post has links to other resources on the topic as well.
Good Luck,
Matthew
Information in article includes :
Bugs
HIG
Lite Versions Internet
Connectivity (excellent information you might be surprised to read)
Excessive Bandwidth Usage Over
Cellular Networks Device Capabilities
(Another great point here that saved me)
- Private API's
- Limited Functionality
- No Interpreted Code
- Handling of UserData
- Copyrighted Content
- Use of Trademarked Images
- Objectionable Content
- UIWebViews
- Transactions Outside The App Store
- Price Information App Icon and App
- Store Image Application Description
- App Store Keywords Updates Are
- Reviewed As New Apps
