I'm at the Edinburgh Intl TV Festival and just got to ask a question to Google CEO Eric Schmidt regarding real names on G+. I asked him how Google justifies the policy given that real identities could put people at risk.
He replied by saying that G+ was build primarily as an identity service, so fundamentally, it depends on people using their real names if they're going to build future products that leverage that information.
Regarding people who are concerned about their safety, he said G+ is completely optional. No one is forcing you to use it. It's obvious for people at risk if they use their real names, they shouldn't use G+. Regarding countries like Iran and Syria, people there have no expectation of privacy anyway due to their government's own policies, which implies (to me, at least) that Schmidt thinks there's no point of even trying to have a service that allows pseudonyms. Unfortunately, the way the Q&A was conducted, I wasn't in a position to ask him a followup on this particular point.
He also said the internet would be better if we knew you were a real person rather than a dog or a fake person. Some people are just evil and we should be able to ID them and rank them downward.
These aren't exact quotes, but I did my best to paraphrase the gist of what he was saying.