Mike Gerra authored a detailed report on semantic technologies and their impact on the Web, particularly the online travel space. It can be purchased via Phocuswright.
The synopsis from Phocuswright:
Social search, which has emerged at the intersection of search and social networking, offers more personalized, targeted search results by focusing them through the lens of user-generated content (UGC), user actions, group interactions and social relationships. The various types of social search are still in their infancy, but they have the potential to respond to travel research queries with highly relevant results. And because social search is targeted to a very specific interest and social group, it may provide an opportunity for travel marketers to more easily identify and connect with well-qualified, brand-appropriate travel buyers.