Let's get out of their way
Absolutely no nonsense when it comes to product design for APPLE. When apple designs a product, they want no interference with the content and the user. No buttons and no unnecessary interface. Apple believes providing a slick and sexy platform and just getting out of people's way.
It allows people to touch the content and feel the product. People should forget about the product when they use it. All the social networks, communities or organizations should be built with such "superb simplicity".
Build a platform and get out of their way. That is the biggest reason why twitter is a hit and so is facebook. And so is orkut not so sexy.