Their product search is... interesting. I used to think that it was programmed by idiots, and wondered how Amazon, with the ability to hire all the expertise in the world, couldn't do better. Then I realised its function is not to give you what you are looking for, it's to maximize Amazon's profits, which it clearly does fantastically well. I would imagine that a lot of heavy-duty machine learning goes into Amazon's product search to make this happen.