I would sum it up as a combination of many factors. One being the presence of a Facebook page with a lot of likes and sharing. Another plus would involve backlinks from Web 2.0 websites. Finally, guest posting and backlinks from high-quality directories and social bookmarking websites won't hurt anything Of course, on top of these things, one would need a lot of quality material, though it seems like I've seen websites with a huge social media presence, but with little content on the actual website. Please correct me if I'm wrong.