It's typically more of a "hit-and-run" type of traffic. Not necessarily low-quality, it's just that people tend to quickly return to their social media, without clicking any ads. And yes, it's probably reasonable to say sites like Buzzfeed have relatively low click-through rates because of that. Google doesn't mind, of course, so long as there's no trickery at work.
Well, ideally, you would want to find a good balance in traffic sources. Having a disproportionate amount of social media traffic could be suspicious for various reasons, and if low-interest, non-converting visitors is all you have to offer AdSense, then it may not be a good fit.
"Having a disproportionate amount of social media traffic could be suspicious for various reasons, and if low-interest, non-converting visitors is all you have to offer AdSense, then it may not be a good fit."
But doesn't that basically describe Buzzfeed, Iflscience and probably Huffington Post as well.
And if primarily getting traffic from social media is a problem what is the answer for larger sites or is there not one? I am sure iflscience would love to get 15 million or so monthly pageviews from google search to somewhat even out their traffic sources. But to some degree whether ifl (or buzzfeed or huff post) gets that traffic is somewhat in the hands of google. And its hard to know if that much traffic from google even exists for those types of topics.
Disproportionate, to me, would be something like 90%+ social traffic, consistently. A majority for social traffic is not in itself a problem, of course. But rest assured those sites you mention get plenty of traffic from search engines and referrals.
I have heard that adsense doesn't like social media traffic in that they consider it low quality traffic.
I don't know where you heard that, but it has not been my experience. Doesn't matter so much where your traffic comes from if it's good quality traffic - preferably that actually buys things from your advertisers. It's not so much Google that you have to keep happy, it's the advertisers.
I should have added to my previous post about "disproportionate" amounts of social media traffic that, as netmeg rightly notes, it still won't be a problem if it's quality traffic, i.e. if there's genuine interest in your content. I was thinking more about how having "too much" social media traffic, and hardly any search or referral or direct traffic, could be a sign that something fishy or unusual is going on, like social spam or click-bait or what have you.
Anyway, those threads you refer to are not about traffic from social media, they're primarily about "invalid traffic" figures. Then someone comes in and says "it's social media!" and "it's your friends clicking your ads!" and now you're worrying about your social media traffic. Don't. Does social traffic lead to more invalid clicks? Possibly. People accidentally click ads more often on mobile devices. That's only a problem if you can help it.
Use common sense. If there's a significant clawback at the end of each month, you obviously need to be paying attention. What's significant? That will differ per type of site, device, and, indeed, source of traffic. 50%, as I saw someone write in one of those threads, is clearly an issue. I'm used to single-figure percentages, usually around 0.5-2%, and wouldn't worry unless it consistently went above 10-20%.