Recently Elsevier sent Academia.edu numerous take down notices for published articles that authors had posted onto their pages in academia.edu. Elsevier claimed breach of copyright. There has been a lot of fall out over this http://scienceblogs.com/confessions/2013/12/10/around-the-web-elsevier-vs-academia-edu-vs-researchers/
Is ResearchGate next? What will you do if RG start removing your published papers? Does it bring into focus just who does 'own' your work?