A _changing_ public system. You put your phone number into your address book. You sign up for a Gmail address. Fast forward one year, these items are suddenly combined without warning.
Brin's "confession" has something to do with it because he was instrumental to creating it in the first place, and someone with the power to correct many of the problems if he wanted to. Instead he's washed his hands of it, and left a segment of his users in the lurch.
If "Igor Partola" is your real name, I think statistically there's a good chance that you understand this innately.
Now, you can argue that the trust was misplaced, or that the author's use of the word "trust" to describe the basis of their users's relationship with and affinity for Google, but I think this is a quibble. It's straight-up goodwill that has been squandered, and it is not in Google's character to admit failure (Scorpion and the Frog), which further corrodes the connection between the company and its users.
"What did you expect?" Yeah, well screw you, too. If Eric Schmidt wants to tell us that if we don't want to use our real names and stuff on Google+ that we don't have to use the service at all, then hey, "I'm a step ahead of you, bub." That's why this article exists, and that's why Sergey is slithering away from G+, and that's why Vic Gundotra left, and at the end of the day Google has a massive failure on their hands and they have too much money to even countenance facts. What will be the Information Age equivalent of wearing Kleenex boxes on one's feet?
"I have nothing to admit," said Gilles Deleuze once upon a time, but the market has eaten up large companies before. While Google-large falling by the Internet wayside would be fairly seismic in historical terms, it would happen slowly enough for nobody to really notice. People already talk about the ins-and-outs of Facebook, it's not a huge jump for them to start talking about the ups-and-downs of DuckDuckGo. Google's already helping that happen by converting Chrome's address bar, where grandmas the world over type what they're looking for, into the browser's search field.
Youtube gets bought by Google. G+ happens. Suddenly Bob is being forced to use his birth name on his Youtube account. If Bob is unlucky his current name or his birth name are outed. While it shouldn't matter if people know that Bob is transgender we live in a world where people are beaten or killed for this.