An interesting counter-example is Goodreads.com. The number of features on the site is amazing, and consistently growing. At a first glance it seems to be a fa

An interesting counter-example is Goodreads.com. The number of features on the site is amazing, and consistently growing. At a first glance it seems to be a fairly basic site for book reviews, but the deeper you dig you find a full fledged used-book exchange, quizzes, lists, comparison shopping, profiles, trivia, quotes, videos, short stories, etc. I'm not sure how they manage to keep it all under control or how they decide which features will be useful, but they do a great job with keeping users engaged in multiple activities on the site, no feature seems neglected or empty.