One could argue that we've been influenced by ads for centuries, and the concept of targeting isn't new. But this is one of the cases where a change in amount (how detailed targeting gets) becomes a change in kind. Yes, it looks like the same thing as before just with more data, but it's actually a fundamentally different kind of thing.

Every time we make a discovery or invent a new tool we play around with it for a while, exploring its uses and implications, and find its boundaries. Atomic energy for example. Before we knew exactly what radioactivity was Marie Curie carried around bottles of highly radioactive stuff in her pockets, she was so nonchalant about it that now her notebook has to be kept in a lead box, 100 years later. Since then we've created power sources and weapons and had disasters. Now everything highly radioactive is regulated and tracked.

We're in the "Marie Curie" stage with our advertising tools. We will need to dial back how nonchalant we are about employing these tools against others eventually. Either it comes from within the industry, or it comes from regulation, or we devolve into a dystopia where companies more and more literally own your mind.