“If you build your application with features based on a user’s location, make sure these features provide beneficial information, if your app uses location-based information primarily to enable mobile advertisers to deliver targeted ads based on a user’s location, your app will be returned to you by the App Store Review Team for modification before it can be posted to the App Store.”

Original article: developer.apple.com
I’m not too sure how this will affect existing applications or whether they’ll be pulled from the Appstore. But if you’re building mobile apps for the iPhone bear this in mind.