Dark Social Rises?
This is an interesting take on how our social metrics may be failing us, by undercounting the sharing that happens outside of social media. Still, I wouldn't start assuming that all of your direct traffic is actually "Dark Social" until you take a look at your campaign tracking strategy; it could be your email newsletter or your RSS feed that's sending this "direct" traffic... or it might actually be Aunt Marge sending you a link.
Here's a pocket history of the web, according to many people. In the early days, the web was just pages of information linked to each other. Then along came web crawlers that helped you find what you wanted among all that information.