I am, and was, a big fan of Tripadvisor. I don't know how many travel decisions, be it destinations, hotels, or even restaurants on site, have been influenced positively by that site. In the past years, I started skipping the top 10 recommendations (like restaurants for example) - there is a "being on top of tripadvisor" business logic that doesn't necessarily mean you will get a great experience - only one that is created to "hack" the platform. In essence, it is a similar problem that Facebook faces - too much scale. As a million member service, Tripadvisor worked great. Now, with half a billion people on it, this scale is a problem - network effects take over. Lenghty, interesting article, especially if your try to transfer the content to any other industry / service that might "scale too much".