ResearchGATE was founded in 2008 by Dr. Ijad Madisch, an award-winning scientist who earned his M.D. and Ph.D. from the Medical School of Hannover, Germany and currently performing research at Harvard Medical School, Sren Hofmayer, who earned his M.D., from the Medical School of Hannover, and Horst Fickenscher, a computer scientist who earned his graduate degree at the University of Passau, Germany. The background of the founders helped them recognize the specialized needs of scientists and scholars, and according to Madisch the site has been built to address those needs.
Of course, ResearchGATE isn't the only social networking service aimed at academics - Epernicus is another such example. It seems clear that there's an opportunity for such a network; I often hear from our researchers that existing social networks such as LinkedIn and Facebook don't meet their needs.