Adblock only helps a little. For example, unless you use a VPN, your ISP knows every site you visit. If you have a debit card your bank knows where you spend your money. Retailers can figure out a lot about you from your spending habits e.g. Target figuring out when someone was pregnant. Facial recognition is growing in use to track people in stores and malls.

We are still in the early days of commercial data analysis. Online retailers and ad brokers (e.g. Google) have been the trailblazers. But it will spread. Imagine a combination of facial recognition and data analysis being used in the real world to serve you custom billboard ads or to allow sales people to remind you that you probably need to buy new shoes.

Lets move beyond sales in to really creepy territory. Want to intimidate someone? Get hold as much of their marketing data as you can, it'll probably be on sale from some data broker. If its not on sale, bribing someone will probably get you what you want. Now let your target know that you know where they shop, what they buy, what websites they visit and maybe they have a drink problem they want to keep hidden. If you think that what legitimate businesses can do with your data is bad, imagine what criminals could do.