I've been considering creating this particular thread for a while, and then Myke Cole posted an interesting article about Social Media. Check out the article here.
To summarize: an editor paid Myke a compliment, saying he's an example to other authors of how to do social media right. In response, Myke says he isn't really aware of what he does, but that he does notice some habits he has, which he lists for the benefit of other authors.
Now, those habits aren't very special. Don't get me wrong, they make Myke a great person to follow, but most of them are based on common sense. For example, I think I keep to most of the same habits with the official Ranting Dragon twitter account. One could say every author should read that article and follow those rules—which is true. However, I believe most authors already do so, simply because it makes perfect sense.
To me, what makes Myke an example to other authors—because I do agree that he is—is the fact that he has a social presence, combined with the fact that he has a lot of social charisma. What makes a difference in my opinion, is that he cares enough to let his fans hear from him every day. It's the fact that he puts thought into what he posts on Facebook, Twitter, and his personal blog (and possibly in more places, but those are the three places where I follow him). He is an example, because he has an open line of communication to his fans.
This is something I've been noticing lately. For example, I see Mark Lawrence post birthday wishes on people's Facebook walls, or Michael Sullivan join discussions on Reddit. I see Sam Sykes make fun of everyone on Twitter, and authors like Anne Lyle, Peat Brett, Mazarkis Williams, and Teresa Frohock have a serious presence there. Because of this, these authors are on my radar. I pay attention to what they say, because make time in their busy schedules to talk to me. I want to buy their books, because I like them. In return, I see each of these authors get a lot of attention all over the web.
My conclusion: Online charisma makes a difference for an author's popularity and, hopefully, in their book sales.
I do think online charisma makes some difference. But for me, I'm not active enough on social media for authors' online presences to affect me much directly; it's the friends I hear talking about the authors that make more of a differene for me. The author him/herself talking doesn't affect me as much as the other people talking about the author. And no or little online presence is much better than a bad online presence.
I tend to find authors either via the library or via friends, review blogs, etc. However, after that I'm liable to start reading the author's social media. That means I'm more likely to buy their book immediately upon it's release if I like what I've been reading online since I read the last one.