Here is a a really good commentary on Google Plus (G+). I have to say that analyzing such a large system and a phenomenon involving millions of users is kind of a fools errand. (Remember "Everything is Obvious"). Still if you are interested in the evolution of social networks it is a good read:
"Is this Google’s swan song? Of course not. But it is almost certainly their biggest failure by a good distance. And it’s not a Flubber-like experimental miss like Orkut and Wave and the many Labs projects snuffed before their time. It corrupted Google’s primary mission, angered users, and eroded trust. Maybe the worst of it is that Google+ could have been so good. It could have been so Google.
But a series of poor choices, misjudgments, and plain stubbornness resulted in the poor thing being sent alone and friendless into bloody battle with an entrenched and veteran opponent.(from Google+: The Charge of the Like Brigade)
A good read. Recommended.