backdraft7 - 12:51 pm on Jul 26, 2013 (gmt 0)
who or what limiting the amount of visitors?
...and this is where we get ridiculous by speculating the 'who' or 'what' part. G does not want us to know. The whole M.O. of "quality updates" is to confuse blackhat (and even whitehat) SEO efforts. I'm done chasing rankings...now I just put my 'thang' out there and let G do with it as they will.
That said, yes, publishers could be a factor, so are mobile users, social media, the weather, you name it.
Bottom line is that (in my vertical) the natural traffic patterns observed 2000-2010 are gone.