You might not notice them unless you’re looking for them, those little white boxes mounted on poles high above the street, at corners where guns and crack pipes hold more sway than police. All day and all night, from gang hangouts in Bayview to the open-air drug markets of the Tenderloin, the cameras are rolling—all 71 of them.

Trouble is, the surveillance cameras the city has been installing since 2005 just don’t seem to work. “After the cameras went up, the guys on the corner just moved up the block,” says the owner of a business near one of the more notorious drug corners, who refused to be identified for fear of retaliation. “I don’t see any difference at all.”

Nor, more or less, did a group of UC Berkeley researchers, who conducted a recent San Francisco–sponsored survey of 19 camera locations. While they found that some theft decreased within 100 feet of the cameras, violent crime levels didn’t budge. In fact, all the cameras managed to do was push the violence down the block: Between 2005 and early 2008, murders within 250 feet of the cameras plummeted (from seven to zero), but between 250 and 500 feet away, they rose the same amount (from two to nine). These were preliminary findings, but nobody seems to expect the final report, due any day now, to be much different.

Mayor Newsom, whose office didn’t respond to a request for comment, has said he will reserve judgment until the report comes out. But his new crime czar, Kevin Ryan, a former U.S. attorney who was forced out during last year’s White House–led purge of its top cops, thinks live monitoring might lead to more arrests. Now, largely because of civil rights concerns, nobody is watching our cameras in real time, so police can request footage only after a crime has occurred. (And that footage, due to storage limitations, often looks more like an art project than a legitimate law-enforcement tool.) But Newsom opposes the idea, and it might not work anyway.

Numerous studies have shown that monitored cameras have a limited impact. They seem to make people feel more secure, even if they aren’t actually any safer. Says District Five supervisor Ross Mirkarimi, who spearheaded the city’s camera regulations, “They have a bit of a placebo effect, and that’s worth something. But we need to decide if this is just about setting up scarecrows, or if it’s about assisting in deterring arrests and prosecutions.” If the public wants to monitor the cameras, Mirkarimi adds, we’ll need to talk about how to protect civil liberties. If that happens, get ready for a nasty, drawn-out fight—San Francisco takes its liberties very, very seriously.

All of which begs the question: Is the program’s million-dollar cost worth it, especially given that this city faces an enormous budget shortfall—one that’s 300 times that amount? Perhaps that money would be better spent on more police foot patrols, or even improved lighting, a deeply unsexy measure that has nevertheless proved to reduce crime by 20 percent. “If you’re trying to stop homicides, throwing money into security cameras is one of the least effective things you can do,” says the ACLU’s Mark Schlosberg, author of a recent report on the use of surveillance technology in California.

Ironically, it’s not police or prosecutors who seem to be ben­efiting most from the all-seeing eyes in our midst—it’s the San Francisco Public Defender’s Office. So far, surveillance footage has helped dismiss the cases of at least three clients, according to Lea Villegas, a spokesperson for the public defender. There’s no better alibi: Caught under the camera’s unblinking gaze, the accused obviously couldn’t have been committing a crime somewhere else. “I don’t think that was the intent of the cameras,” Villegas says with a laugh, “but they’ve been pretty useful to us.”