This is the kicker when it comes to the advertising industry. Advertisers pride themselves on slurping up all the personal information they can get their hands on, telling their customers it will help make their advertisements more effective. But anyone who uses the internet (without an adblocker) can tell just how poorly implemented, targeted, and ineffective those ads often are. On top of it being incredibly difficult to measure advertising effectiveness. It very much feels like a whole multibillion dollar industry (which created several megacorporations) is selling a whole load of bullshit, and causing great harm to a lot of people in order to justify it.