The expectation of FB is very different. A normal user would assume that the ranking is based on a news link popularity: sharing, clicks or some other user metric.
https://en.wikipedia.org/wiki/Jane_Akre#Whistleblower_lawsui...
This article helped me to better understand some of what's going on:
"Agnotology ... is the study of culturally induced ignorance or doubt..."
And the biggest issue I have, is that as far as I know, from January 2014 to present, Facebook's help page was written in a way to mislead users on how trending topics actually work [1]. From reading that help description, most users, including me, imagined Trending topics to work as /u/cft described. Yet that page has no mention that every single trending article on Facebook is curated by a human. How is that not an enormous oversight?
[1] https://www.facebook.com/help/737806312958641 How does Facebook determine what topics are trending?
> Trending shows you topics that have recently become popular on Facebook. The topics you see are based on a number of factors including engagement, timeliness, Pages you've liked and your location.
> On a computer, the topics are grouped into 5 categories: All News, Politics, Science and Technology, Sports and Entertainment.
What if a larger proportion of Facebook users are younger, which typically leans left, and therefore left news trends more? Oh, wait it is that way...