Apple has revised the rules and review policies of the App Store. The changes bring with them a renewed and greater weight on paid apps in the app review process. As it now stands, users can no longer provide reviews for apps obtained via promo code. In other words, if you're downloading a paid app for free or on promotion, you won't be able to review it. That privilege is now reserve for paying customers only.
Apple says the changes were needed to help level the playing field. That is, no longer can developers flood the market with free promo codes to bulk up the number of favorable reviews the app boasts in the App Store. For the time being, however, the new policy appears to be implemented in a less than consistent fashion, as some paid apps delivered by promo code are still allowing users to rate their experience of the app. Still, the change has definitely taken effect for no shortage of iPhone and iPad applications.
An official response from an iTunes support, received by a forum-goer over at iOS games site TouchArcade, notes the change, saying that the company now requires ratings and reviews of applications to be done by paid users, keeping those who may have installed the application from a developer's promo code from contributing to its aggregate rating or written review log.