In Chap. 1, it was elucidated that SNS is often used by young people at the time of a product purchase. Using real data, Chap. 2 demonstrated that there are some pioneering conceptual models of information communication that consider the effect of SNS in Japan and these concepts are valid. The marketing and science research group sponsored by the Japan Marketing Association (JMA) measured the effect of blogs quantitatively as well as qualitatively over two years, that is, FY2006 and FY2007. Given that SNS consisted mainly of blogs prior to the emergence of Twitter and Facebook, measuring its effect is significant even today when it comes to reviewing the role of SNS. In this chapter, literature related to the Internet will be reviewed and the effect that the quality and quantity of blog posts have on purchasing will be checked using the data from this study group.