Amazon and Google ... have built their brands on the power of their filters ... Google's search algorithms [and] Amazon's recommendations ... are nothing more than the wisdom of the crowds, the statistically measured opinions of millions of ... people. That's why we trust them.Chris makes a great point. The power of people drives Amazon's and Google's systems. Algorithms may sort, sift, and aggregate the data, but the source of the knowledge is the actions of individuals.
Some talk about social software as if it is unique in the ability to tap into the wisdom of the crowds. Sharing is explicit in social software systems -- people have to explicitly state relationships and explicitly share recommendations -- so perhaps it is not obvious that there are more subtle ways to share this knowledge.
Systems like Amazon's recommendations and Google's PageRank implicitly share the wisdom of the crowds. Collaborative filtering-based systems like Amazon's recommendations use algorithms to find people with similar interests and share their wisdom. Google's PageRank algorithm mines the link graph -- links people made between web pages -- to surface authoritative and useful sources of information.
Implicit systems like Amazon's and Google's surface the wisdom of the crowds anonymously, quietly, and with no effort from users.