Whether it's a "failure" or not seems debatable. Does anyone even remember the name of Apple's social network?
The original Apple evangelist Guy Kawasaki has nothing but good things to say about it:
http://mashable.com/2012/05/22/guy-kawasaki-google-plus/
And before you jump to click "Reply" with some comment like "But he's selling a book!", take a moment to consider who you're writing about. That's Guy Frickin' Kawasaki. He hardly needs the money.
Agreed. The poster I have been discussing this with in this thread pronounced Google+ not just a failure. But a stinging failure. It's WAY too early to "call it." And quite honestly - even if it doesn't succeed - referring to it as a stinging failure seems a tad biased whether it's now or later.