There are three types of word of mouth in terms of directionality: positive (a recommendation), negative (advice against), and neutral.
Neutral, you ask? Sure. Imagine a friend telling you that a new bike rental stand will be set up outside your place of employment. You drive a car and have no interest in riding a bike. Well, that's your problem. But you probably don't care one way or another about that piece of information your friend passed along to you (and which you might pass along to another friend at work who doesn't own a car) - it's neutral. But from the marketer's perspective, that information could be disseminated through a relatively inexpensive advertising or direct marketing campaign. What is interesting when it comes to efforts to leverage WOM is a positive recommendation. And the following infographic neatly summarizes a few key points about it.