I must say that i just took a class that discussed Semantic Web (the professor actually is currently doing research in that area) and I am not a believer... I definetly see the need for a global "tagging" system, I just do not see anything out there that will actually do it at the moment in any type of useful way. My professor's research was on using XML and RDF and just for simple document it would take way more processing power than the finished product would be really worth. At the moment I am more inclined to believe that customer tracking/history is where we will be headed for a long while (hence your google example, or amazon which if you are logged in and are a frequent customer can be quite scarily accurate at "knowing you" and your tastes).