"Tell me any place, and I guarantee you there's a camera there somewhere," says Selevitch, president of the security company CEI Management Corp. and founder of the website www.bostondetective.com, which represents a consortium of licensed professional investigators in the Boston area. "If you want to get technical about it, you're pretty much under surveillance all the time."

Video surveillance has taken off in recent years, thanks to smaller, less obtrusive cameras and rising security concerns since the Sept. 11 terrorist attacks. Customers at banks, retail stores, and other businesses have long been filmed in an attempt to thwart crimes and solve them once they occur, but in recent years, camera surveillance has also made inroads at places such as churches, parking garages, and supermarkets, Selevitch says.

Statistics are elusive. The trade organization ASIS International, which lists 33,000 members and calls itself the "preeminent organization for security professionals," says nobody tracks numbers of surveillance cameras in the U.S., though it has commissioned a study to be completed by September to measure the worldwide scope of the security industry. Latanya Sweeney, director for the Carnegie Mellon Data Privacy Lab in Pittsburgh, a think tank on the relationship between technology and privacy, says she's not aware of any such figures.

In an unofficial count last April, two members of the Surveillance Camera Players, a New York-based group that opposes the use of surveillance cameras in public places, toured Boston on foot to spot and map cameras they saw installed in public places. Armed with binoculars, the pair led six people on a survey centered in the Financial District that located 128 such surveillance cameras. Ten were in or on government buildings, the group found, while 110 were on private property. Six other cameras were on tall buildings or otherwise elevated high off the ground, while two more were on street poles -- and who knows how many more were not noticed.

Selevitch says there are parts of Boston where nearly all of the streets and sidewalks are covered by video cameras. Based on his work over 25 years in Boston, he estimates that 80 percent of the streets around the Federal Reserve and South Station are covered by cameras, along with perhaps 70 percent of the area around the Downtown Crossing shopping district.

Those percentages will almost certainly rise, he says, particularly since most new buildings built in Boston are covered by exterior cameras. "Cradle to grave, you're going to be on camera all the time," he predicts.

Sometimes actions recorded by cameras in public spaces end up on the Internet. The Data Privacy Lab estimates there are 10,000 webcams now broadcasting images to publicly available websites on the Internet, settings that range from beaches to university campuses to cityscapes.

One such website, EarthCam.com, allows Internet surfers to view a host of live shots of Boston at any time, day or night. Taken by a camera on top of the Prudential Center, they include Fenway Park, the State House, and the Common. Another camera shows live scenes at the corner of Washington Street and Temple Place in Downtown Crossing. Boston University has several live cameras around campus. There's also one in the office of a man named John Lester who works at Massachusetts General Hospital.

It's difficult in some parts of Boston to walk or drive even a few blocks without being filmed. The Big Dig already has 200 operating cameras, and 200 more will be running by the time the project is finished in a year and a half. The Massachusetts Port Authority uses about 400 cameras, most of them at Logan Airport.

On the roads, 27 cameras monitor intersections around Boston, and another 15 are being installed. Jim Mansfield, spokesman for the city's Transportation Department, says the cameras monitor traffic so signals can be timed to improve the flow. The cameras aren't used to catch speeding cars or red-light scofflaws, he says.

MBTA passengers better get used to smiling for the camera, too. The T currently has 79 cameras, which are located at a quarter of its 60 or so underground subway stations, with another hundred planned as the subway system largely switches to automated fare collection early next year. John Hogan, Jr. , chief of the MBTA's operations control center, says every one of the stations will have a camera and most will have several. He says the cameras will save taxpayers' money by making T riders more likely to pay the fares if they know a camera is watching.

Jeffrey Parker, the MBTA's director of subway operations, says the cameras make the T safer by taping scenes that police can review after a crime has been committed to find suspects and witnesses. The cameras also make the T more efficient, Parker says, by allowing dispatchers to spot groups of waiting passengers and redirect trains accordingly.

"From the control center, it's not important to us what someone's face looks like or what color shoes they're wearing, but we do want to see how large a crowd is," Parker says.

Businesses that use video cameras say they're an indispensable tool to prevent crime, ensure the safety of customers, and keep crime-related losses, which customers would ultimately have to pay for, at a minimum.

FleetBoston Financial uses surveillance cameras at all of its 427 ATMs and 71 branches in the Boston area, says spokesman Jim Schepker. He says the cameras stop crimes before they happen and help investigators nab suspects when one has been committed. "We believe surveillance is a way to discourage the criminal element," says Schepker. "It's invaluable to investigators."

Beware 'mission creep'In some quarters, though, the camera eye's quiet spread is raising alarms about privacy.

Carol Rose, executive director of the ACLU of Massachusetts, says she's concerned about "mission creep" -- cameras that are set up for one purpose, such as catching traffic scofflaws at an intersection, and are used for another, such as identifying participants in a political rally.

"The question is, who's looking at the pictures being taken and how are they using those pictures?" says Rose. "The cameras don't distinguish between the good guys and the bad guys."

The group has been vocal in its concern that the USA Patriot Act threatens civil liberties by giving new surveillance and other powers to law enforcement agencies. On its website, it warns, "The United States is at risk of turning into a full-fledged surveillance society. George Orwell's vision of 'Big Brother' has now become technologically possible."

"We have a situation where the government is increasing its power to watch the citizenry while diminishing the citizens' power to watch their government," Rose says. "The concern is that surveillance cameras that go up be used for the stated purposes they go up for, and not to invade people who have the expectation of privacy."

Boston-area YMCAs have taken their own step to protect against invasive surveillance. The use of cellular phones with cameras was banned last year from the 12 branches of the YMCA of Greater Boston, which host 100,000 visitors per year.

YMCA Vice President of External Affairs Kelley Rice says it was common sense, not any instance of locker-room mischief, that sparked the ban. "You always see stars in embarrassing situations whose pictures end up somewhere," she says. "You could see the potential for a problem here."

A war room on highStill, in a darkened room filled with 42 giant television screens, John Hogan Jr. is watching. Eight floors above the Financial District, in a nondescript gray building on High Street, the chief of the MBTA's operations control center looks down from what he calls the "war room."

Below him are the screens, each one 5 feet tall and just as wide, a curving, constantly shifting array of lights and images that dwarfs any department store's TV showroom. Most of the screens -- 38 of the 42 -- resemble enormous video games, with orange arrows depicting trains moving slowly along the tracks. Lighted icons show track crossings and emergency exits, while another screen shows the Weather Channel.

But it's the three camera-fed screens that catch the eye, rotating every few seconds from one station to the next in live, constantly changing glimpses of subway life. One follows the Blue Line. Beach Mont. Revere Beach. Another works its way up the Red Line. Harvard. Porter.

Hogan says later this year, all 42 screens will be equipped to show live feeds from the cameras.

As he speaks, a blond woman in a black waist-length coat appears on one of the screens, talking on a cell phone and apparently unaware that her image is being viewed 10 miles away. A caption says the woman is standing on the inbound platform at Suffolk Downs station. In the war room, three workers talking on phones and monitoring the trains' progress pay her little attention.

Just off the MBTA's war room, seven videocassette recorders run 24 hours a day, seven days a week to record images from the cameras. Tapes are kept for 30 days in case police need to review them to investigate a crime. The cameras do not have microphones.

The MBTA is by no means alone in its increasing use of cameras. Other public agencies such as the Boston Transportation Department, Massport (which operates Logan Airport), and the Turnpike Authority (which oversees the Big Dig), have installed cameras or are adding more to improve traffic and boost security.

Hogan says the MBTA isn't interested in using the cameras for passenger surveillance. He says he's more interested in preventing toll-cheaters through the cameras' presence, or in using the cameras to redirect trains to cut wait times for passengers who have better things to do than wait for a train.

Last year, a man fell onto the track at Broadway station and a sharp-eyed dispatcher saw it on camera just before a train rolled in. He quickly halted the train, and the fallen man was helped back onto the platform, uninjured.

"The guy was lucky because he was right in the middle of the track and the train would have made contact with him," says Hogan.

Behind him, a screen switches to Wood Island station, where a young man in a blue-and-white plaid shirt and black winter cap gazes blankly across the tracks, unaware of the camera perched above him a few feet away.