When Facebook announced its new App Center last month (and again when they finally launched it earlier this week), they chose to focus on its reliance on user ratings in order to determine the visibility of apps. They clearly stated that only "high quality" apps will appear in the App Center, and the measure of quality would be based on user ratings and engagement.
For users, this means that they may not even see apps that habitually receive low ratings from other users - which is no doubt a good thing. For developers, it means that good work can be rewarded and crappy work, well, may not even get invited to the party.
But naturally, user ratings can be an tricky metric. Not only do you never know which users actually took the rating process seriously and which users are simply bitter for bitter's sake, but users ratings are prime territory for manipulation.
And though a Facebook product manager tells Inside Facebook that they are "considering options for allowing users to rate apps directly from the App Center page," it's not currently possible to rate any app in the new App Center on demand.
Every user rating so far has been based on a random sample.
If you go to an app in the App Center and hover over the star rating, you can see a breakdown of how many votes the app has received as well as the breakdown (1-5 stars). But you can't vote on it. That's because Facebook purposefully randomizes app voting in order to avoid manipulation and attempt to provide accurate ratings - or as accurate as you can ever expect from user ratings.
According to Inside Facebook, the random app rating prompts can appear in the recently used app area below a user's bookmarks, or on the right-hand side of some pages. Although asking a user to rate an app as they are in the process of removing it seems like it may bias the results a bit, Facebook is apparently still prompting this type of rating - but in a sparse, random manner.
Considering that Facebook made a point to talk about how ranking in their App Center would rely so heavily on ratings and engagement, it's nice to see a system like this in place. It helps make the concept of the user rating trustworthy, which is something we can't say for all platforms.