Disclaimer: I don't care what is or isn't a factor... just so long as there is data to support it either way. So in that spirit I will share some data.
Meta Keywords Factor Overview
Myth 1: Fear the competitors
First, I have seen the argument "Don't use meta keywords because competitors can see what you target" many times. This argument is BS in my mind because if what you are trying to rank for isn't obvious on the page already I bet your rankings really suck for it. Sure there are black hat ways of sculpting anchor text to rank for a term that is not on page but that isn't the usual whitehat case. So if you have a whitehat site I can't see any competitive disadvantage to using meta keywords... it is at worst harmless.
Example: If your webpage is about cats I will still know it is about cats if you don't use the meta keywords otherwise you probably won't rank for cats.
Myth 2: Everybody knows it doesn't do anything
Really? These websites must have missed the memo.
Walmart
<meta name="keywords" content="online shopping, shop online, electronics, home furnishings, baby gear, toys, video games, walmart, walmart.com"/>
Amazon
<meta name="keywords" content="Amazon, Amazon.com, Books, Online Shopping, Book Store, Magazine, Subscription, Music, CDs, DVDs, Videos, Electronics, Video Games, Computers, Cell Phones, Toys, Games, Apparel, Accessories, Shoes, Jewelry, Watches, Office Products, Sports & Outdoors, Sporting Goods, Baby Products, Health, Personal Care, Beauty, Home, Garden, Bed & Bath, Furniture, Tools, Hardware, Vacuums, Outdoor Living, Automotive Parts, Pet Supplies, Broadband, DSL">
Overstock
<meta name="keywords" content="best price, wholesale, discounts, deals, cheap, online store, online shopping, name brand, merchandise, liquidate, liquidator, sale, lowest prices, low prices, savings, free, bargains, values, bedding, furniture, electronics, jewelry, watches, apparel, overstock, overstock.com, o.co, o.com">
QVC
<meta name="keywords" content="qvc,qvc.com,
www.qvc.com,online shopping,qvc shopping"/>
Safeway
<meta name="keywords" content="Safeway, ingredients for life, weekly specials, recipes, pharmacy, eating right, store card, print coupon, diet recipes, signature cafe, about us, quick links, services, company info, our brands, shop online, low prices">
All these websites have the budget and the rankings to suggest they have best in class SEOs helping them. Maybe they know something you don't.
Myth 3: It doesn't work anymore.
View attachment 96952
It still correlates with rank position frequently. It isn't the strongest signal. I suspect it still counts as extra matches on page and affects your search relevance slightly with those extra matches. Go read about TF-IDF on wikipedia to see how the math works.
I certainly invite everyone to show data that it doesn't work. Please let it not be quotes of other bloggers opinions. Real data please.
Myth 4: There is no benefit to using it
Besides the fact that there is certainly no harm in using it ... besides the correlations with rankings that appear frequently for it... you absolutely can use it to stay organized and track which pages are targeting which terms. Then when you run your SEO robots output a column for URL and Meta Keyword and you have your rank tracking list for intentional SEO (the SEO you do on purpose versus the SEO you get by accident which is what most people find in their rank tracking). So even without a ranking boost there still may be advantageous ways of using it.
Conclusion
I don't care if it is or isn't a factor but based on the data I would still use it. It is easy to implement. It is at a minimum harmless. Likely correlates with rankings for adding extra keyword matches on page. If you practice intentional SEO it is a great tool for staying organized. Finally, massive online retailers still use it. Maybe they know something you don't.
P.S. If you like the spirit of this factor overview let me know and maybe I will write more.
