One of Google+'s key distinctions isn't a lesson from Facebook, but from Twitter. On Facebook, communication is initiated via the two-way act of friending people: for each connection, requests are sent and then either approved or denied. On Twitter, things are more open: anyone can follow anyone unless that person explicitly declares themselves private. Twitter's openness makes the site a pure platform for sharing thoughts and ideas, while Facebook's gated community makes deciding what to share a delicate balancing act of restraint and exhibitionism.
Google+ seeks to exploit the best of both worlds. Anyone can follow anyone on the site by adding them to their circles, but individuals still have tight control over which of their posts are seen by whom. You can take to the site and make a declaration that the world can see (without even being limited to 140 characters!), or share a personal reminder with your favorite couple to meet up for dinner.
In this way, Google+ has positioned itself as the social network that lets you portray all facets of yourself online without ever needing to compromise. It's a powerful premise... and this is only the beginning.