Commentary - Invited Comment on "Opinion Leadership and Social Contagion in New Product Diffusion"

Iyengar, Van den Bulte, and Valente (2011; referred to as IVV in the rest of this paper) address a number of important questions in their paper, “Opinion Leadership and Social Contagion in New Product Diffusion.” They have assembled a unique data set in which they are able to observe not only adoptions and network ties, but also marketing effort and two different potential measures of recipients’ leadership, one self-reported and the other sociometric. Their paper delivers a number of important and interesting results: (1) contagion exists even after controlling for many possible confounds including, most significantly, marketing efforts; (2) contagion is moderated by the recipients’ self-reported opinion leadership: opinion leaders are less responsive to the actions of others; (3) this is not true of sociometric leadership (indegree); (4) contagion is moderated by usage: adoption by a heavy user has a bigger impact on her ties’ decision to adopt; and (5) time of adoption is increasing in both indegree and self-reported leadership: influentials adopt earlier. Their paper promises to contribute to the evolving literature on word of mouth (WOM), and wordof-mouth marketing, in a number of ways. In this comment, I offer some opinions on where the paper stands in this literature and, perhaps more important and I hope more interesting, where the literature itself stands. The authors ground their inquiry in a set of three fundamental assumptions. I will discuss these assumptions that motivated their work and offer my perspective on IVV’s contribution to our ability to have faith in these assumptions. I will particularly highlight where I feel there may exist deeper, unanswered questions. I feel it important to stress that it is not my goal to write a review article on contagion or word of mouth. My goal is a simple one: to emphasize the contributions offered by IVV and to note the very real potential their paper offered to shift the focus of future researchers in the area. The authors argue that the field of word-of-mouth marketing is characterized by three assumptions. I address each of them in turn.