You jest, but I fear we're not far from chemical analyzers being put into the sewage system, so that advertisers can detect a sudden appearance of e.g. pregnancy hormones in someone's toilet output, and helpfully spam them with baby stuff ads.

I remember reading about work to build something like that in public toilets to detect potential infections spreading around a city, but I'll be voting against such projects up and until the adtech industry is burned down to the ground.