Jyri Engestrom has posted this presentation about social objects. What most struck me was his argument that a lot of talk about social networks focuses on the links between people, but doesn't attend to the social objects through which they connect. Successful entrepreneurs are good at creating objects that are obligatory points of passage, or obpops. Google is - for now - a phenomenal obpop.

It also links to this Youtube satire on the friendships Facebook offers:

Hat tip: Adriana