To be fair, it is actually a valuable economic service to predict which ads will be most relevant to which customers. Assuming a rational consumer that is. An irrational consumer can be mis-served by being shown ads for things he doesn’t need, but a rational one only benefits from some third party making effort to locate ads they’ll likely respond to.

Advertisement is just networking for market information. It’s a problem when people get badly influenced, but that’s a corrupted side path. The default path is a person being connected with useful information that increases the expected net present value of their money. It changes the decision tree, and the new tree resolves to a higher expected value.

Assuming the decider’s ability to make optimal decisions on any given tree, of course.