I just recently learned about ACR. My first thought was to set up an LG TV in the basement and stream non-stop p0rn for 3 months or so. Then see what ads start showing up for me. Like, I wonder if there's a target group called "Creeps addicted to p0rn."
just to clarify: ACR is actually not taking a screenshot, it calculates a fingerprint of the picture and sends it to a server.
The fingerprint is then checked against a database of some common content, to understand whether you're watching some Movie/Series on DVD/BluRay or with an external set-top-box.
Not sure if porn is even fingerprinted in that database, would probably be 100% more fingerprints... /s