Came across a company that uses PostRank as a trademark, here is a thought:

In the API they like to mention about Feed Rank (two words) probably because it is too cumbersome to rank every single post and it doesn't make sense either when you are dealing with real-time data.
 
FeedRank is a concept that works in an environment that ranking posts individually is not possible or at least no longer effective, a post can inherit the rank of its feed instead. There are metrics other than post itself that could determine the rank of the source.