Hey @joshuad31 - welcome to the forum! This are very good thoughts on online identities.
I think it is a little bit easier to get Circles started since I expect that people will connect to each other mainly based on “real world” relationships.
It is also noteworthy that Cirlces does NOT solve the sybil problem in general. There WILL be sybil accounts. However - the good thing is that every single user is not (negatively) affected by sybils unless they directly “trust” a sybil or trust a group that contains sybils.