Word of mouth is a form of promotion in which satisfied customers tell other people how much they like a business, product or service. Personal Influence: The Part Played by People in the Flow of Mass Communications , Katz and Lazarsfeld found word of mouth influence to be far more important than advertising or personal selling. The word of mouth conversation is the best feedback you’re ever going to get. It’s far better than any other kind of market research, because it is the authentic voice of the consumer. Read more »