Can we agree that marketing, while currently crude, does have some effect? Some people are more swayed than others by bought-and-paid-for messages. But right no

Can we agree that marketing, while currently crude, does have some effect? Some people are more swayed than others by bought-and-paid-for messages. But right now mass-marketing is pretty lowest-common-denominator. What happens when it gets cheap enough to dedicate one-humanish-intelligence 24/7 dedicated to learning about how to influence you to buy or vote. Monitoring what you look at online, where you go, people you frequently engage with, etc., and customizing/"fabricating" interesting "news" to consume, etc.. And then what happens when it is a trivial cost to put 1,000 human-intelligences working against you? Or maybe not you, but all of your neighbors or 25% of the citizens in your country?