[snowwrestler]

Google has been upfront about greater use of learning AI (as opposed to hand-tuned algorithms like PageRank) to index and rank their search results. In order to return a good result, a learning AI system must first be trained on what a good result looks like. Since search returns results to humans, humans have to provide the guidance on what is a good or bad result.

Often an AI can be trained by a corpus, like training a spell correcter by feeding it the text of a dictionary. But the data that Google works is the entire web, which changes all the time, so they need constant feedback on what is good or bad.

Google also personalizes results now, so the AI needs to learn not just what is a good result, but what is a good result for that particular person, given everything else the AI knows about that person. That would require inputs from a wide variety of people.