This is an interesting and new approach for a review system (in this case, rating applications,) since users cannot rate applications on-demand, but rather have to be randomly presented the opportunity to rate them. This can prevent a lot of fake and malicious reviews.
Currently there is no way for users to rate an app on demand. Instead, users are randomly prompted to provide star ratings through modules around the site. This unique approach discourages user or developer manipulation. Facebook product manager Matt Wyndowe tells us the company is considering options for allowing users to rate apps directly from an App Center page, but Facebook wants to do so in a way that maintains the integrity of its ratings.
Because high ratings can lead to better placement in the App Center, developers want to know how to get more positive ratings for their app. Although there is no particular link users can visit to rate a Facebook application, we’ll go over the different ways that users are currently able to rate apps.