Whenever I write about surveillance issues, I usually hear some variation on the arguments that (a) only people who have something to hide should care about privacy, and (b) blanket surveillance is just the latest law-enforcement tool, like fingerprinting or DNA testing, and anyone who questions it is a silly technophobe.
Those arguments rely on some false assumption. Everyone cares about some degree of privacy and dignity. As Cory Doctorow pointed out in the Guardian back in June: "I know what you do in the toilet, but that doesn't mean you don't want to close the door when you go in the stall." And constant monitoring of a population is entirely different from looking for evidence—such as fingerprints or DNA—after a crime has been committed.
But the more fundamental question is why surveillance matters to all of us, whether or not we think we have something to hide.
There are lots of ways to answer this question: chilling effects on free speech, erosion of intellectual freedom and democratic debate, a culture of mistrust (which is bad for civic engagement), the threat of discrimination and selective enforcement (especially when the watchers have little or no oversight), a false sense of security about our ability to identify and prevent threats, the possibility of ongoing and systematic violations of the Fourth Amendment, and so on. (To learn more about surveillance, its harms, and how quickly the technology is outstripping the law, you can start with this article and this response at the Harvard Law Review, as well as this one in the Berkeley Technology Law Journal.)
Those are serious issues, but a little complicated to explain to skeptics with short attention spans.
First: Once the tools are in place, they don't go away. Even if we assume that surveillance technologies are installed by entirely virtuous people for virtuous reasons—that's a gargantuan "if," with a lot of evidence to the contrary, but stay with me—there's no guarantee the people controlling that technology in the future be as virtuous.
That's why we need to have a serious public conversation and establish some very clear rules about how new surveillance technologies should and shouldn't be used—with very real penalties for people who break those rules.
Second: Unchecked surveillance turns us all into perpetual suspects. It casually, at the discretion of a very few individuals, short-circuits over 200 years of work at trying to build a fair American justice system. That system isn't perfect, of course. But there are reasons why it was designed to include judges, warrants, probable cause, and other checks and balances.
Who are a few people at the NSA, or a few detectives at a local police force, to decide that we don't need that anymore? Who are they to override over two centuries of American jurisprudence?