Yesterday, Google shared on the webmaster blog their 2015 webspam repot. They said they served up 4.3 million manual actions in 2015 and as @TheRealpmac calculated, that comes out to about 500 manual actions or Google manual penalties an hour!
As he said, there is "nothing manual about that." Truth is, many of those may be hacked notifications that probably are somewhat automated. The discussion of if manual actions are automated is something I dove into with caution a month or so ago.
Why so many manual actions? Well, in 2015, Google saw a 180% increase in hacked sites in their indexed, so they used both manual actions and the hacked sites algorithm to reduce them from showing up in the index. Don't you worry, it is still a serious issue in 2016 so they have more work to do.
Google also said they "saw an increase in the number of sites with thin, low quality content. Such content contains little or no added value and is often scraped from other sites." Google said they "sent more than 4.3 million messages to webmasters to notify them of manual actions," and "saw a 33% increase in the number of sites that went through spam clean-up efforts towards a successful reconsideration process." So verifying your site in the Google Search Console is important.
Google received more than 400,000 spam reports and acted on 65% of them, and considered 80% of those acted upon to be spam.
There is lots of webspam out there and it is a battle every day for Google.
Forum discussion at Google+.