The concept of Whuffie is that of a sort of "cultural currency"; that is, how good a person's or organization's reputation is. Ms. Hunt is obviously a veteran of the Web, and she makes some good points - in essence, that one needs to be honest and moral in order to achieve high Whuffie rather than just try to use the Web as another outlet or venue for typical one-sided marketing hype.
No argument there; certainly if we could all check our egos at the door and put out honest appraisals of products (including our own, including admitting when we screw up) then it will engender more positive feelings on those that wander around the WWW to shop, etc.
I didn't rate the book higher only because I get the sense that Ms. Hunt thinks that the Web is the be-all-and-end-all of the world of commerce. Certainly, many people (myself included) log on multiple times a day, but nevertheless I don't think of my online presence as the essence of me. Too, there are still many people who either never get to the online world at all or else only sparingly, preferring "real reality" to "virtual reality" and so not so absorbed in what happens online.
So as a general instruction guide of how to do good online, this book is fine. As an attempt to prove that it is (or will be in the foreseeable future) critical to enjoy high Whuffie levels, it falls way short.