Of course, which is why I never implied that they don't have drawbacks. Just that the drawbacks of this method, in the context of privacy and tracking, are much more numerous.

>And I want to reiterate that you don't know how prone this new technology is to false positives, you don't know how cheap it can be made.

I don't know how cheap it will be, that's true (it's probably more expensive, in time and money, than an air tag or pin camera). But it is pretty easy to figure out that this will have more false positives than every other current tracking method. Give me an air filter and 30 minutes to walk through a store, and I can make it look like dozens of people were in places they never were. That's not an issue with any other method, especially considering the effort to produce false positives by a bad actor is ~0.

>Just to illustrate, instead of figuring out how to put concealed cameras in the entries of a building, could it be enough to place a small device near the ventilation exhaust fan?

Even if we ignore the false positives and difference in cost, this wouldn't let you pinpoint timing, any other information about the person that might be valuable (who else was with the person, what they were wearing, etc.), has a risk of contamination, doesn't have the ability to give real-time results, no option of capturing audio... Probably several other downsides I'm not thinking of immediately.

Again, I'm not saying that this technology is completely useless. Just that, compared to all of the technology already invading your privacy, this technology is a large step backwards in practically every privacy-related metric.

Raising a fuss about stuff like this is how ordinary people get fatigued by "privacy nuts" and stop caring about the dozens of technologies and policies which are significantly worse, which are already invading our privacy.