I wonder how plausible it would be to deduce where a given webcam is (some combination of IP data, context clues, visible landmarks, maybe face searching) and then contact the owner to let them know. There used to be this fun site called where-is-this.com where people could share images of public places for others to try to track down; it would be nice to harness something like that for good.
I feel like I’ve read about three letter agencies using the humming of power lines to geo-locate where a video/audio was recorded.
“Electrical Network Frequency (ENF) analysis”.
I’m going to dig more and will leave some links when I get back to a computer.