I don't see any contradiction between the semantic and the user-centric web. They work in different domains. Content and connections, technical and social, order instead of noise. The semantic web aims to improve the degree of order in content while the user-centric web (as subdomain of the synaptic web) focuses on the connections in between. I wonder if any of these is addressed in David Siegel's book.

I'd question the viability of the Authority model. On the web authority is more and more being replaced by transparent credibility. Clay Shirky calls this "algorithmic authority" in http://www.shirky.com/weblog/2009/11/a-speculative-post-on-the-idea-of-algorithmic-authority/. He says: "As more people come to realize that not only do they look to unsupervised processes for answers to certain questions, but that their friends do as well, those groups will come to treat those resources as authoritative." If I write an article on heart transplant and I'm a transplant surgeon at Beth Israel Hospital I don't need third party certification. If I write a blog about the future of social media, my online presence (tweets, posts, replies) will justify my credibility, and again, there's no need for third party certification. In the first case my authority is obvious. In the second however, it's so not obvious that even a professional reviewer has no more (or better access to) information to rely on than anyone else. I think there's only a very narrow segment of content providers where this model makes sense. And I bet that those to whom it does will hardly be willing to pay for such a service.