> I get shown ads for products I just purchased. All this spying, machine learning, big data result in "he bought a mattress, show him more mattresses".

You know, I had a really long argument about a decade ago with an Amazon senior engineer on the ads side of things about this. I was complaining about repeatedly being shown ads for the same blender I had just purchased (not accessories, not competing products, the exact same blender). And I hit a brick wall of "everybody complains about this, and we've been trying to change this, but every change to this makes the metrics worse".