without getting into too much about how I can put icons to documents and people right on my Windows desktop and Android start screens, my amateur psychologist thinks that the reason people-centric UI design hasn't taken off is that we subconsciously associate functions with people. In other words, our interface with another person centers around the functions that person supplies us with. For example, I have a few friends that I only ever play online games with, so my functional connection to them is via games or game-centered social networks. I think "play games with..." first before I decide on a person to play with.

This is why it's natural to chart out social relationships as entities/nodes for people and relations as modes between the nodes. Navigating to another person involves traversing this graph over a selected relation.

I think this is the reason I go to facebook before I think about posting something on a friend's wall, or open up my email client, or picking up a phone first, before finalizing my internal decision on who to call.