For those of you optimizing your News Feed distribution, Facebook just pushed an update tonight that changes the way application feed items are displayed to users without the app.

Essentially, feed items that link to pages that require adding the app to view will now get much lower Feed Rank than feed items that link to pages that can be viewed without adding the app. Facebook writes,

We hope that this change will improve the quality of our user’s experience when interacting with News Feed stories for Platform applications. While this change will in the short term result in fewer application stories being displayed (since most of them currently require that users add the app), we expect that it will eventually enable us to show more application stories as the quality of this experience improves.

Facebook says that for now, this change will only affect News Feed stories for users who haven’t yet added your application, “but in the future it may also affect the rank of your story for users of your application.”

Considering Facebook’s philosophy toward the News Feed is important in planning your application’s approach to viral distribution. It’s clear that Facebook favors applications that expose pieces to users without the app.

Update: Also, starting tomorrow night, Facebook will prohibit News Feed stories that contain the word “message” in either the application-generated or Facebook-generated parts of News Feed stories. According to Facebook, “Use of the word ‘message’ was confusing users into thinking unauthorized people had access to Inbox messages.” However, user-generated content that includes the word “message” is still permissible.