Tom Standage summarizes his point best early in the book:
The Romans did it with papyrus rolls and messengers; today hundreds of millions of people do the same things rather more quickly and easily using Facebook, Twitter, blogs, and other Internet tools. The technologies involved are very different, but these two forms of social media, separated by two millennia, share many of the same underlying structures and dynamics: they are two-way, conversational environments in which information passes horizontally from one person to another along social networks, rather than being delivered vertically from an impersonal central source. (...) (Such) social-media systems arose frequently because, for most human history, social networks were the dominant means by which new ideas and information spread, in either spoken or written form. Over the centuries, the power, reach, and inclusivity of these social-media systems steadily increased. But then, starting in the mid-nineteenth century, everything changed. The advent of the steam-powered printing press, followed in the twentieth century by radio and television, made possible what we now call "mass media." These new technologies of mass dissemination could supply information directly to large numbers of people with unprecedented speed and efficiency, but their high cost meant that control of the flow of information became concentrated in the hands of a select few. The delivery of information assumed a one-way, centralized, broadcast pattern that overshadowed the tradition of two-way, conversational, and social distribution that had come before. In the past decade, however, the social nature of media has dramatically reasserted itself. (...) The Internet has enabled a flowering of easy-to-use publishing tools and given social media unprecedented reach and scale, enabling it to compete with broadcast media and emerge from its shadow. The democratization of publishing made possible by Facebook, Twitter, and other social platforms has been hugely disruptive for mass-media companies and, more importantly, is beginning to have far-reaching social and political effects. The re-emergence of social media, now supercharged by digital networks, represents a profound shift not just within the media, but within society as a whole. (Tom Standage, 2013, pages 3-4)
He then goes on to describe in detail how (social) communication has worked and changed over time, for example: wall posts in Pompeii, Cicero's (and other roman writers' and politicians') use of distributed and shared/commented letters, Christianity's use of shared and distributed letters, Martin Luther's use of the printing press and how his theses went 'viral', Tudor England's use of shared poetry to built personal profiles at Court ("The use of social media for self-expression and self-promotion is nothing new, but dates back at least as far as the Tudor court of the sixteenth century." Tom Standage, 2013, p.81) and coffee houses of the seventeenth century as discussion platforms.
He contrasts these examples with the mass media model developed in the 19th century. In his view "the broadcast model considers the role of the radio listener and television viewer to be merely that of a passive consumer. This is as far as it is possible to be from a media system in which people create, distribute, share and rework information and exchange it with each other. It is the opposite of social media." (Tom Standage, 2013 p. 213). Social Media is thus in essence nothing but the reinvention of the norm - at a technically more advanced level. Or in Dick Costolo's words, Twitter's chief executive in a 2012 speech at the Gerald R. Ford School of Public Policy (as quoted by Standage, 2013, p. 233): "... in the Agora we had an inside-out view of the news. It was the participants themselves who would come there and talk about what was going on with them or what they had just witnessed or what they just saw (...) and Twitter reinvents the Agora" - as opposed to an outside-in view of mass-media broadcasting.
Almost as an aside Tom Standage (2013, p. 8-13) also touches on the argument of the importance of grooming as a way of social interaction and continues to discuss the Dunbar Count. This could be a point of inspiration for our bachelor and master students looking for an interesting research subject for their respective theses.
In summary, Tom Standage's book offers a very readable introduction to the history of media from a perspective of how the creation and distribution of media content was socially motivated and organized. It is fun to read, informative and for all those, who need further motivation to have a look into this book: it's an excellent source for many a small-talk snippets when yet again the virtues of Facebook and Co. are being discussed over gin and olives.