It seems to me that "social media" has done more harm than good for writing. I mean, a lot of authors really capitalize on it, using their Twitter streams and Facebook pages to engage with fans and build a massive following. There are authors like John Scalzi and Charles Stross who build an intelligent and dedicated following on their blogs (honestly, I think Scalzi owes more to his blog than to his books for his preeminence in the sci-fi field), but it's important to note that they have been at it for a long time (Scalzi was blogging, and also writing professionally, before he was a published novelist), and they make their blog content interesting in itself, not just because you happen to be a fan of the author. Authors who just create Facebook pages and Twitter accounts because nowadays all the agents are saying you need a "platform" seem likely to do themselves a disservice.
( Why I don't Tweet and my Facebook page is boring. )
( Why I don't Tweet and my Facebook page is boring. )