A Walgreens at 23rd and Mission Streets, another stop that night, is well equipped with cameras, too. “At least two in the pharmacy, the entranceway, probably over the shopping aisles,” said Phil Caruso, a Walgreens spokesman. “We like those, and some of the ones on the exterior, to be visible, and we put a sign in the front so people know they’re being filmed.”

Like many other big stores, Walgreens often has other, smaller cameras about door height, to catch faces in case the police want close-ups of people.

Target was not willing to talk about what my thief bought with my card, or its use of video, but it may be the most extensive watcher of all. Just the checkout area of its store at Fourth and Mission Streets in San Francisco, the most likely location my thief visited, has at least 18 cameras, from four manufacturers.

The thief spent almost $200 at Target, enough to afford nine of the 13 different home video surveillance cameras Target sells there. That would have involved walking past another 50 highly visible surveillance domes.

The advent of cheap home cameras, and the theft of packages delivered from the likes of Amazon, have led to an explosion of video in San Francisco. Police officers investigating a serious crime have been trained to look for nearby cameras, and every one of the city’s 10 police districts has a specialized video surveillance officer.

Once you become aware of their ubiquity, looking for cameras can be chilling fun. I counted 15 on the block going away from Target. That may be a bit high — five of them were trained on the entrance to a medical marijuana store. Of course, everyone with a smartphone is also packing video capability.

The San Francisco Police Department likes this video deluge, according to a department spokesman, Carlos Manfredi, because things like credit card fraud are often linked to other crimes. “We’ll circulate pictures of people to all the stations around town, to see if other officers know the person from other crimes,” he said.