I give Google+ six months.
Check out this post from Mashable, which headlines the claim that somewhere around 75% or more of Google+ users are male. That in itself may or may not be a problem but here's what is a problem and something of a buried lede: Mashable claims that 60% of users identify themselves as web developers or software engineers. In other words, Google+ is a very niche community.
Social networking sites, by definition, can't take advantage of Internet Long Tails. They need the network effects of the Fat Body, or whatever you call the left-hand side of the graph. There's almost no such thing as a sustainable niche social networking site.
But...but Google+ has shot up to 5 million users! Great. That leaves them only 745 million behind Facebook and somewhere in the hundreds of millions behind Skype and Twitter. How long do you really think even this pace of adoption will continue? (How many web developers are left unsigned-up?) In the world where Google+ is trying to compete, 5 million puts you way closer to the Tail than the Body.
Granted, Google+ is still in its invitation-only stage, but that model in itself has proved problematic for Google. Remember Google Wave?
I think the world at large has social media fatigue. Very few civilians are really looking for another social media network to join, even if it has a few features that would be better than what's on their current networks. Who's got the time, other than, well, web developers and software engineers?
Six months. Nine months, tops.
