Some of the things under development are quite amazing. For example, there is a biometric face scanner that can pick out known bad guys in a crowd. The Transportation Department is reportedly considering the development of a “dataveillance” program (in Rosen’s terminology) that will review travelers’ real-estate histories, living arrangements, and similar personal data, so that it can assign them color-coded risk levels–red, green, and yellow. There are fingerprint scanners, iris scanners, and even brainwave scanners somewhere in the pipeline, which can be hooked up to sophisticated databases or lie detectors as the case may be. And up atop the indignity index sits a machine tested by Orlando International Airport that would deliver a buck-naked image of each passenger who wanders under its microwave gaze.

Are you outraged at the thought? I have to confess that I’m really not. Like many Americans, my first reaction to this James Bond-style technology is to embrace it, in the hopes that someday it will save my skin. As for the intrusion, it hardly bothers me; I figure I have nothing to hide. This is a trusting, optimistic, intuitive view of the world. The question posed by The Naked Crowd is whether that view is very smart.

The book seems to have inspired by a challenge posed by Rosen’s fellow law professor, Lawrence Lessig, who several years back, called Rosen a technophobic “Luddite” for expressing concerns about the widespread installation of surveillance cameras in Great Britain following the wave of I.R.A. terror in the early 1990s. Lessig suggested that, rather than reflexively resisting the spread of such new technologies, Rosen should pour his efforts into designing a technological and legal approach to surveillance that would protect both security and liberty. In answering this challenge, Rosen concluded that his first order of business should be to persuade skeptics that a balanced approach is actually necessary.

As a skeptic myself, I have to say, he’s pretty convincing. Part of the trick here is that Rosen steers almost entirely away from partisan arguments, instead approaching the subject with courteous engagement. (Memo to Hannity, Lowry, Coulter, Moore, Franken, et. al.: You’d be surprised at how far this gets you.) But the bigger trick is in the breadth of Rosen’s approach.

Rosen starts with the demand side of the equation, observing that the drive for increasing levels of surveillance is fundamentally driven by public opinion. That’s generally consistent with democratic principles–but as a practical matter Rosen argues that this can produce some very bad decision-making. “[P]ublic fear,” he writes, “leads people to react to remote but terrifying risks in emotional rather than analytic terms.” Borrowing from the work of sociologists and psychologists, Rosen argues that the public doesn’t really understand probability or statistics. Instead, it focuses on dramatic images–like a plane crash or collapsing tower–and panics. The government responds in kind by producing regulations that ineffectually address visually memorable past events–for example, by banishing nail clippers from commercial air travel after September 11–while ignoring more significant but ordinary perils like the double fatburger you are about to eat for lunch.

But, the skeptic asks, so what if panic drives us to over-surveillance? Are the costs that great? And aren’t there checks and balances to protect us?

The discussion of costs is a particular strength of The Naked Crowd. Rather than simply assert that surveillance technologies are “creepy”–the standard fallback of privacy advocates–Rosen lays out the threats that inadequately restrained surveillance can pose, even to those who have nothing much to hide.

Rosen is concerned about the potentially dangerous concentration of information in government hands. He worries that by eroding the old barriers of law and technology that historically discouraged the prosecution of trivial offenses, we will begin to feel like we live in a police state. (This sounds hyperbolic, but if you have ever received a ticket from a stoplight surveillance camera, you know there’s some truth to it, at least at the emotional level.) But most of all, he is concerned about the possibility that vast government databases will classify citizens by risk category, and that these classifications will affect our freedom of movement and even our equality of opportunity.

Think about the huge life events and decisions that hang on the strength of your credit rating. Now, what if the government were to give us similar ratings? And what if for some seemingly arbitrary reason (a skinny-dipping citation, a few unpaid parking tickets, or an expired dog license) you wind up in a second- or third-tier classification? In a sense, argues Rosen, “risk profiles extend harms similar to those imposed by racial profiling across society as a whole, creating electronic layers… that determine who is singled out for special suspicion by state officials.”

That actually sounds worse than creepy. And as Rosen describes the situation, not enough stands between us and that future. For one thing, he argues that the exhibitionist strain in contemporary American culture reinforces popular indifference to privacy. And even though many surveillance technologies could be rendered privacy-friendly with just a little tweaking, he notes that technology companies don’t develop them because there is insufficient demand. Finally, he points out that because constitutional doctrine in this area is less far-reaching than one might imagine (the law doesn’t demand that a search’s scope be proportionate to the severity of a crime, and doesn’t recognize any privacy interest in data held by third parties), the courts probably won’t, and in Rosen’s view shouldn’t, get ahead of public opinion as champions of privacy.

This leads Rosen to look toward Congress as the last and best hope for striking an appropriate balance between security and privacy. He would like to see a congressional committee permanently empowered to review executive branch surveillance for effectiveness and intrusiveness. This committee would be charged with investigating alternative technologies which could produce similar benefits with lower privacy costs. In short, it would supply the checks and balances on the government’s surveillance powers that are missing in the current system.

This seems like an appealingly sober, balanced, non-hysterical recommendation. If there’s a problem with Rosen’s analysis, then, it lies in his point-blank assertion that there is no appropriate role for the courts in this area even if Congress fails to act. “The excess of the crowd are the Achilles heel of democracy to which there is and should be no judicial remedy,” he asserts.

Well, not exactly. The Constitution was written to ensure that public opinion cannot simply trump certain minority rights unless it is amended through a pointedly burdensome super-majority procedure. And while Rosen makes the good point that judicial law-making in areas like abortion has provoked unfortunate political backlash, it’s not at all clear that this situation requires the same interpretive leaps that the Supreme Court made in its reproductive rights cases. Indeed, one would think that there may be some room for leadership by the courts in this area. After all, the Fourth Amendment prohibits “unreasonable searches and seizures,” and the Framers did intend it to limit broad, untargeted intrusions into the private sphere. There’s also a question about whether public opinion is as polarized on this issue as abortion. As Rozen himself suggests in The Naked Crowd, the public may just be poorly informed.

But of course, that’s what makes Rosen’s contribution so worthwhile. Drawing on law and science, psychology and sociology, The Naked Crowd tells a convincing story about the world we live in, and a cautionary one of the world we may be entering. It is all the more laudable for doing so in a steady, nuanced voice that one hopes will rise above the noise of the crowd.