Maybe it is because almost everyone has a Facebook page and Twitter page and there so many other types of different social networks out there because the internet is becoming more and more of an influence on people by making it easier to communicate to one another and so people may have embraced those networks a lot more recently.
Social networks have always been a significant aspect of our culture. However, more recently the abundance of digital social networks has become more apparent. The importance of social networking has been promoted since, I believe, the industrial revolution brought more power to corporations. This established a "who you know" process of professional advancement, and this has not changed nor was it a recent development.