Most people didn't have a "Google account". They had a GMail account. If they had Blogger or YouTube accounts, they usually had them before Gmail.
It was bad enough when Google started shoving those accounts into one and tacking services on people didn't ask for without politely asking them to sign-up. But now they are forcing people into an entirely new service that has the explicit purpose to expose them and to annihilate their privacy.
I wouldn't mind the principle of one single account for all Google services in principle, if a) I can have multiple accounts, b) such an account can be know as "honeybooboo666", and doesn't need my real name or phone number, and c) that account does not to automatically sign me in to services I didn't sign up for and I don't want to use on that account.
The latter is especially important so that anything "honeybooboo666" does on YouTube isn't accidentally registered under my other accounts of MyJob@BigCorp and MyRealName@Family
That's why people have separate accounts. honeybooboo666, MyJob@BigCorp and bowlofpetunias are very different entities, and trying to "out" them all as "MyRealName who works at BigCorp" is just not on.
Rewrite history much?
Every platform Google ever acquired had it's own login, and Google didn't have a login for a loooong time.
But all of that is besides the point. This is not about SSO, this is about an SSO fully integrated with a service geared at destroying anonymity and privacy.
I wouldn't mind a single Google login if that was what it was: a login, a username and password. Google+ is so, so much more.
So: I'm sorry. I did mess this one up. I don't think, however, that my mistake was actually important from the perspective of the article. I've been using some of the services people are saying had third party login support now for many many years, and unlike YouTube I do not remember ever seeing any kind of disconnection between account models used on each. Maybe they were just integrated faster, or maybe its because I had a YouTube account that was ancient and had options that others long since did not.
But either way: it doesn't seem like SSO is an argument for Google+. Google already had single sign on, and to the extent to which it ever had separate login systems that it maintained for its acquisitions they were all rapidly merged. Maybe even in the case of YouTube (which I still feel was different, give that as recently as a year ago I remember still having the ability to manipulate my underlying YouTube account).
Forcing the account to use G+ does make it get forced to use the underlying picture and name from the other account. I can see that as being vaguely interesting. But that goes beyond a "unified login/account system".
I don't understand how this wasn't the case before Google+. I've had my Google account for years and it always worked on all the Google services I've seen. I've never had to use a separate account for anything.