He talks a lot about anonymity and privacy. For example, you are never so anonymous as you are on a crowded street. Sure, people could look at you, but why would anyone look at you in particular? And it's usually more embarrassing to get caught looking at another than to be looked at. It's the safety in numbers argument. Another way of viewing that problem is to imagine being the only one on a nude beach wearing a bathing suit. More people would look at you then than if you were in the buff as well (the bathing suit being a metaphor for a "wall of privacy").
He reckons the concept of privacy will continually be distorted to the point where only those who can afford the most expensive encryption will be able to enjoy it- ie privacy will be a luxury. The Mafia, the State and Mega Corporations will be able to enjoy total privacy- from you and from any other source of accountability- but the average Joe won't be able to have any privacy at all.
Another key here to is if we equate secrecy with privacy. There is a subtle but distinct difference between the two and he does a pretty good job illustrating that difference and spelling out the implications of legislating for one's perceived right to secrecy when we should rather protect privacy instead.
For sure, it's a sticky issue (privacy/secrecy and technological advances). Brin offers a pragmatic look at the problem that doesn't sit will with everyone but he does have a point when he says this phenomenom is coming and short of banning all further advances in certain fields of technology, there is practically nothing we can do to stop it. Better, perhaps, to come up with solutions that allow us to work and live with the technology (if it's inevitable anyway) than to revert to Luddism. In a few more years, the gov't will have deployed cameras that you won't be able to detect- they'll be too small. What are we going to do then?