#nymwars, noisy content (with poor controls), confusing UI, and intent that was expressly counter to users' interests really didn't help.
See Tim O'Reilly's Aug 23, 2011 post requesting topics for conversation with Bradley Horowitz:
https://plus.google.com/104092656004159577193/posts/A1qHbykj...
As I commented recently on a private re-share:
What's telling to me are:
1. How many times Real Names / Nymwars came up.
2. The alienation issue: how Google were (and frankly, have) demolished goodwill with their core tech evangelist community (I used to be one, I no longer am).
3. How lacking Google's first instance of G+ was: no search. For reals.
4. Requests that remain unanswered. Especially subscribable circles / feeds, RSS, and tags.
5. How many names I recognize here. Many are in my Circles. A few are long gone.