Fred Wilson had a great post today about the evolution from the OS to the browser to the search engine to ... the new dimension whatever that is. Better put, Fred does not believe that search itself is not the ultimate component of the relevance vector. He believes in user preferences, behaviors, cached information (including cookies), etc.
However, there are many sophisticated Internet users that constantly clear out their cached browser information, or setup their browsers not to receive any cookies (yours truly included). For these types of users, the relevance vector needs to be made up by something else. And even if one could observe certain behavioral patterns, and start creating rules, there are many things that don't quite work on the web (for instance, imagine the difficulty in trying to guess estimate the probability of a user actually buying something on the web, depending on the number of ads he/she clicked on). So this will not be an easy endeavor by any stretch of imagination. But it is an interesting line of thought... and food for some future posts!
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