This mirrors what a Volokh Conspiracy post called "the longstanding division between those who endorse an absolutist interpretation of libertarian principle versus those who take a maximizing approach." Mangu-Ward can't see a gray area in the loss of privacy due knowledge of one's activities becoming so much more widespread, so it's no problem. Reasonable libertarians like myself do see a problem, and while the solution is less clear, acknowledging a problem is the first step.
I'm not going to deny the advantages of cameras. I think a camera trained on a bicycle rack increases liberty by allowing people to ride bikes that don't get stolen, more than it decreases liberty by monitoring people for the brief time they're locking their bikes (I've had many bikes stolen over the years). Carefully targeted cameras might be the solution.
More broadly, I think the loss of privacy might possibly be inevitable, and it might not be all bad - maybe we'll learn to be who we are and not care who knows about it. But pretending there's no problem with this future, and therefore doing nothing to nudge the future in the right direction, is simplistic.
P.S. Some discussion of reasonable libertarianism over at Kevin Vrane's renovated digs, No Se Nada.
P.P.S. In Mangu-Ward's defense, she evolves partially beyond simplistic libertarianism in the Op-Ed she wrote on the camera issue:
The New York police recently announced plans to create "a citywide system of closed-circuit televisions" operated from a central control center, funded primarily by federal antiterrorism money.She needs to keep moving in this direction.
Admittedly, this is where the surveillance nation gets dicey. Concerns about misuse of public cameras by authorities are reasonable, and violations should be punished. Several cases now wending their way through the courts are expected to set standards regarding proper uses of, and punishment for abuse of, surveillance.