Arguably Google+'s Circles were pioneered by XMPP thanks to roster groups (https://tools.ietf.org/html/rfc6121#section-2.1.2.6), which can be used for PubSub to only allow members of a given group to retrieve elements from a given node. So you'd publish stuff for your friends group, for your family group, ...

They did, and we felt like it didn't work because it gave people too many choices. They had some suggested circles, but we felt that if we simplified the logic of separating your life, it would make it easier to use and require less thought when connecting with people.