Earlier quoted context omitted.
While that is to an extent a hindrance, it is also an opening. Social groups in real life are relatively contained. Facebook just mushes it all together. This is one of the few things Google+ got right, with asymmetric relationships and ease of controlling who sees what. While Google+ "failed", that's the attack angle I'd take if I wanted to go after Facebook: Look for ways to let people better limit sharing, to enco…
I think most people she want to share a pic and tag their friends. I don't think people want something so complicated.
As for "most people" wanting something simple: I'd argue that most people have something far more complex today: People sign up to multitudes of sites and create different identities for e.g. dating, different forums, their regular circle of friends. People often go to great lengths to separate them. People even often have multiple accounts on the same sites.
Sites like Facebook stubbornly trying to get people to tie everything to a single name that they're know to by everyone is fundamentally flawed for this reason, and it will always present a barrier, and it's something that's exploitable if someone comes up with the right model to start eating away at them at the fringes.