The surprising impact of word of mouth marketing in a digital age

Mark Schaefer
6 min readAug 28, 2023

Ed Keller is one of my marketing heroes. He’s considered the godfather and preeminent authority on word-of-mouth marketing and he wrote the seminal book on the subject in 2003, The Influentials. Ed is still researching the subject today as a professor at the University of Pennsylvania.

To illustrate my Ed Keller fanboy level, I used to drop by his office whenever I taught at Rutgers University just for a chance to meet him. I never did. So what a thrill when one day Ed reached out to connect to me on LinkedIn!

Since then, we have collaborated in a few ways, including a conversation within my RISE marketing community.

Word-of-mouth marketing has never been more relevant and never less understood. If this is a new idea to you, this article on the difference between influencer marketing and word of mouth might be a great place to start.

So let’s get to Ed. Here are a few excerpts from my conversation with him and how word-of-mouth marketing is especially relevant in the digital age. These are quotes from Ed, which have been edited for brevity:

What is an influential?

For a long time, we have had a misconception about how influence works. These are certain people — about 10 percent of the…



Mark Schaefer

Keynote speaker, marketing strategy consultant, Rutgers U faculty and author of 10 books including KNOWN, Marketing Rebellion, and Belonging to the Brand!