Law enforcement surveillance requires privacy to be effective
Being watched isn't a neutral state. When someone else--particularly someone with punitive authority--looks at us, the distinction between innocence and guilt shrinks. It doesn't disappear, and there are legitimate societal trade-offs between privacy and the presence of surveillance cameras.
But surveillance creates suspicion, in the minds both of the watcher and the watched. There's enough misconstruing of behavior and intent by law enforcement that the public has a legitimate reason to be on its guard when in the presence of surveillance. Mistakes are rare--but not rare enough.
The typical argument against pervasive surveillance typically breaks down along these lines, that of the right to privacy weighed against the right to public safety. A recent report commissioned by the U.K. Government Office for Science adds a nuance that alters the winner-take-all aspect of the privacy debate in which a gain for privacy is a loss for public safety.
Namely, it finds that too much surveillance has a corrosive effect. It does damage to the "public acceptance central to the UK notion of 'policing by consent.'" At a certain point, surveillance produces diminishing, and then adverse effects. The debate about surveillance isn't a binary one, but one about accommodation, in which privacy is a requisite for law enforcement cameras to be effective in the first place. Law enforcement and privacy advocates shouldn't be viewed as antagonists; each has an interest in the other's success. - Dave