From this article:
Think about how Google works. When you type in a term, the search engine puts the site with the most links pointing toward it at the top of the list. That means bloggers and discussion boards are extremely powerful in influencing Google's search results, because bloggers and discussion-board posters are promiscuous linkers, constantly pointing to things they love or hate.
Doesn't this necessarily mean that Google is constrained to the zeitgeist of the moment? I've been wondering about this for a while and this kind of nails it. If blogging and twittering eventually dominate Internet traffic, how valuable will Google remain? In some ways the Internet is like a global nervous system; are we building something which thinks and reflects, or which twitches reflexively?
(I'm feeling very deep today.)