It's not clear whether this book really grapples with the problem of pseudonymity on the web. What happens when a single user can start multiple accounts--one for good behavior and the other for trolling? When the trolling account gets banned, can they just start another one?
There can be no 'reputation' without an answer to the problem of pseudonymity.
The guys who created the 4chan web board code seem to think that the comment is what should have the reputation, not the user. This is one reason why they have a default-to-anon posting style (With options to force anon only posting).
People then focus on the content of the comment, not the posters aura/name/backing.
One thing I initially hated about HN but have quickly grown to like: usernames are displayed in tiny, faint text. There are no avatar images, signatures, or other visual identifiers. This has a similar, though limited, effect -- it puts the focus on the content, not on the user. (My wife regularly reads my comments without realizing I'm the author; this would not happen on a board with avatars.) Yet it also allows users to build a reputation over time, encouraging us to consistently produce quality content.
When it comes to opinions though it does seem that who says something should play a part. Think of reviews - someone who says something is great and has a history of thinking the same things are great that I do is more relevant to me than an anonymous person thinking something is great. Reputation is a level of relevance that a user can build within a community.
There can be no 'reputation' without an answer to the problem of pseudonymity.