As noted in the Introducing WAM blog in the comments, wikia removed from all wikis Special:PopularPages which previous to that was Special:Mostvisitedpages.
What is a WikiFactor Number?
A WikiFactor number is a determined number from a list made by usually "Special:PopularPages" and it factors two things: the count of pages, meeting up with page views in 1,000 counts. The example screen cap from Shmups Wiki shows that the number is at the 3rd(Article: "Commodore 64") from the top being "4,048 views" while the 4th article ("Otomedius Excellent Weapon Locations") has "3,758 views" which means its a wikiFactor of 3 or shorthand noted as "wF 3".
So here is a table:
|Highest view count Article||Total View Counts for Article||wikiFactor Number|
|1.||1000 or above||wF 1|
|2.||2000 or above||wF 2|
|3.||3000 or above||wF 3|
|4.||4000 or above||wF 4|
|5.||5000 or above||wF 5|
|6.||6000 or above||wF 6|
|7.||7000 or above||wF 7|
|8.||8000 or above||wF 8|
More can be read about this at WikiIndex
Why is this needed?
Ultimately, most wikis compete with other wikis, and WAM does not help wikis that are competing with wikis outside of wikia. There is bragging rights to be had here, and it shows the strength of the wiki's reach. Sites like Wikiindex use the numbers to determine the strength of said wikis.
Why does Wikia not support this great ego building tool of measurement?
Beats me. They assume that everyone at wikia only look at wikia content and forget that there are other wikis that compete with wikia wiki's. They must not care about staying competitive is all I can guess. WAM was suggested some months back would have this feature also, but nothing came of that.
What do I do if I want to have this?
Bug the living daylights (but don't be rude) to Wikia Helpers and let them know you want this back! Get your fellow editors to bug them too. Get a movement started. This is something they can fix at anytime, but have not most likely cause they thought no one cared.