This may have been mentioned elsewhere, but this is the first I've seen it phrased like this: Circles lets your mom expand her universe - In Facebook, your mom

This may have been mentioned elsewhere, but this is the first I've seen it phrased like this: Circles lets your mom expand her universe - In Facebook, your mom tends to limit her universe to friends since... well... Facebook defined connections to others with the term. Google+ doesn't define your mom's relationships - your mom does. The naming of the relationship is a really neat point. Even if you're not your mom and use Facebook to connect with colleagues or acquaintances or investors, they're still weighed down by the baggage of the word 'friend.' Whether or not Facebook has the ability to share with separate groups of people, they're all called the same thing. There's a mental tax here when you have to convert: friends from school, friends from the bar, friends from work, wait, no, colleagues from work. Similarly, Twitter has no labels of importance: you're following someone's tweets, but there's no implied relationship. Lists are one way to add semantic meaning, but you don't use them with the same regularity as your main timeline. Features aside, Google+ strikes a neat balance here with just the ability to label your relationships. No mental tax (unlike Facebook), plus meaningful information (unlike Twitter).