Social websites viewed as games

The Web: Hidden Games by C. Weng
Some websites are designed to be games. Most are not. But have you ever heard people, or found yourself addicted to Digg, YouTube, or Facebook? Have you ever wondered why? Well, it’s because they are games, at least partially! Officially, they are social networks, news aggregators, etc. and not designed as game sites like Second Life is. However, these sites contain all factors of a game. They are not only useful, but also entertaining. You can manage relationships with friends, gain recognition, and even set trends. This book will describe the view of websites as games in general, and then study Digg, YouTube and Facebook as specific case studies. It will show you what the goals of these websites are, how to play, and how to win. Applying the game perspective to more areas of the web, users may find other hidden games and can thus use those sites with greater efficiency. Web designers also can learn from this perspective and use the game design to achieve better results.
An interesting perspective which the writer expands on in a free downloadable ebook (link above). It explains why I'm not really into them, I'm just not a player.