Mike Gerra authored a detailed report on semantic technologies and their impact on the web in December 2008. It can be purchased via PhoCusWright.
The explosive growth of user-generated content, multimedia and vertical data across the Internet has brought a renewed focus to finding new methods of extracting meaningful information. An increasing number of technology companies are looking for ways to add meaning to, or extract understanding from, these vast pools of data. In essence they are aiming to make the Web a meaningful guide rather than a static catalog of information. Over the last several years, this long-term goal has fueled a number of promising approaches to a more meaningful Web, commonly referred to as the semantic Web.