Social Media Silos
Years ago we heard that Facebook was a silo. What was meant by this term is that FaceBook would pull content into its social network and behave like a portal, without allowing people to leave. It encouraged people to see the World Wide Web as Facebook and nothing else. For a while it worked.
Zynga and The Death of Conversation When FB was young, and vibrant it was a network of friends having a chat, until Zynga came along.