The cameras have impressed civil-liberties-minded lawyers. Kevin Bankston, a staff attorney with the Electronic Frontier Foundation, in San Francisco, says, "Any technological measures that can be taken to mitigate the privacy invasion and avoid the chilling of legitimate conduct in public or private spaces that are being recorded is a good thing." The markers are a limitation, he says, but "that's not an argument against this type of research. In fact, it's an argument for this type of research."

Bankston says that laws governing video surveillance in public spaces around the world offer little protection to those concerned about privacy. In a few cases, embarrassing or lewd footage recorded by security cameras has been posted on the Internet. Bankston contends that the overwhelming issue is the unease generated by knowing that someone out there may be watching you.

But even if privacy-shielding camera systems were put into use, there would be great debate about how hard it should be for governments to see fully unobscured video footage. Christopher Slobogin, a law professor at the University of Florida who has written on public camera surveillance, says, "I don't think the government should have to demonstrate probable cause in order to find out the identity of some person." Suspicious behavior, he argues, should be sufficient. He cites Terry v. Ohio, a well-known U.S. Supreme Court case that ruled that law-enforcement officers do not need a warrant to stop, detain, and frisk people.

Goldberg says that there may someday be "legislation where you can put up security cameras, but you have to use the p-chip, some privacy chip that encrypts the face. My hunch is that people will say that's a step in the right direction."