The Wall Street Journal reports that Google+ is essentially dying, with users spending on average three minutes a month there, while they're spending seven hours per month on Facebook. If those numbers are even close to accurate, they're brutal.
The WSJ spins this as Google's failure to differentiate Google+ from Facebook, but it's a mistake to think this is about features. Google+ has failed to date because of network effects. I've signed up for Google+, but I never go there, because no one I know goes there, either. My friends and family are on Facebook, and so that's where I go, too. It's quite simple. If you want to beat Facebook, steal its members. Features are largely irrelevant; what you need is people.
Sooner or later someone will disrupt Facebook -- it's inevitable -- and that company will do it by being cooler than Facebook. The initial community will be high school and college students, who will like it in part because their mothers and grandmothers aren't already there; only later will the numbers grow so great as to attract the less cool elements. It's like real estate: at first the artists move into a neighborhood that no one else likes, and it works for them because it's cheap and filled with other artists. Then the yuppies and the wanna-be's follow the artists into the neighborhood, and the whole thing gets so gentrified that the artists move out and look for the next cool spot.
My guess is that Google made a fundamental mistake when rolling out Google+, in that its initial community (and, by consequence, its initial appeal) was among the tech-savvy crowd. Techies only appear cool to other techies.