I think the underlying problem with G+ is that Google was founded on doing things that people like, and the way they identified what people like was by introspection. Google was run by people who didn't like clutter on web pages, so they found a way to do search, and eventually to make money, by giving the information without irrelevant images or animation. This worked because a lot of people don't want visual clutter, and some really hate it.
It isn't a big problem that Google has defenses against those who try to game the page rank system. Figuring out how to not be evil while dealing with the Chinese government isn't Google's core competency, but it doesn't seem to be wildly out of their range.
However, Google is not set up to handle individual likes and dislikes-- they have non-trivial problems with customer service.
My hypothesis is that folks at google introspected, decided for some reason that they'd prefer to be in a real names environment, and don't have the cultural resources for dealing with customers who hate a product of theirs.
This entry was posted at http://nancylebov.dreamwidth.org/497389.html. Comments are welcome here or there. comments so far on that entry.