We don't know how many total clicks this involves, did the clickthrough rate drop 1%, 5%, 90%? Was the traffic search, search syndication, content? Where there content text ads, image ads, flash ads? Did he ever add new keywords, ads, geographic markets? Did he ever change the landing page design?
I would be very embarrassed if I wrote that blog post.
He explained his methods and gave useful graphs.
Yes, the article could have been more useful. But the way to make that happen in the future isn't to bitch endlessly about people not doing enough free work for you. It's to thank them for the good you got out of it, and politely suggest next time that their article could be even more valuable if they did X.
http://www.evanmiller.org/how-to-read-an-unlabeled-sales-cha...
Blog posts are marketing, he's driving traffic to his site with this blog. and his "facts" amount to squiggly lines. he doesn't deserve to get traffic from this.