In the news now: "Publishers threaten to remove millions of papers from ResearchGate. Take-down notices “imminent” as lawsuit is filed alleging widespread copyright infringement."
See Nature: Article Publishers to order millions of research articles removed fr...
See Inside Higher Ed: https://www.insidehighered.com/news/2017/10/11/researchgate-bows-publisher-pressure-and-removes-some-papers