I think Google+ 's mistake, like the author, has to do with a changing doctrine, but i think it has more to do with a branding issue than an innovation or technology issue. (it could be both, but i would argue perception comes before reality when it comes to success)
I think "Google+ is a dud," has less to do with whether social is broken, but rather with human perception and branding.
Much the way Google owned the category search in peoples minds, Facebook owns the category social in peoples minds.
Google made two fundamental mistakes.
1. Using their brand that stands for Search on something else. The human mind is like wet cement, once a brand owns a category, that impressions is almost impossible to change. (Ever try to change someones mind from his political philosophies? almost impossible).
2. Building a product in a category that is already owned by another brand without positioning themselves opposite it.
This is classic... Burger King will never take over Mcdonalds market share because they are trying to convince people that they are better. Since the category is owned already, they need to claim, "We are different"
When it comes to branding, its all about human perception. Like the authors daughter said, "Facebook is where the people are." Even if that statement weren't true, the perception is ingrained in peoples minds.
A good example of competing with an established brand is Coke vs. Pepsi... coke was the real thing, original coca cola, so pepsi came out and said were for the new generation. Why be old when you can be young and fresh.
Avis didnt say we are better than hertz, they said, sine we are number 2, we try harder.
Dominoes didn't say we have better pizza than pizza hut, they said, we will get it to you faster.
Listerine didnt say we taste better than scope, they said, "the taste you hate twice a day."
This is branding 101.
A brand can only stand for One Thing. (a brand that stands for everything, stands for nothing.)
If google wants to compete in the social game... They either need to create a niche of social like twitter, foursquare, and pinterest did, or they need to use a new brand name, and position themselves opposite facebook, not claim they are better...
Big executives always talk about convergence, but the Human perception just doesn't work that way. When you combine two things, people assume you are compromising on quality on both sides.
When you separate things, people assume you do that one thing much better than everyone else...
Google owned the search brand because that was all they did, Search. The new ways of trying to get into other businesses like Paul Graham said," is a chink in their armor."
Just my two cents.