Commenting on advertising and marketing on the Internet is tricky. On one hand, people don't like having information gathered about them, even if it's anonymous. Having tracking cookies and other files placed on your computer without your knowledge to gather information about you seems to be something that should be illegal. But it's nothing that hasn't been going on since the beginning of business.
Every time you purchase something from a physical store it gets noted. It gets put into some kind of database and when it comes time to acquire new inventory somebody goes over that database and looks to see what buying trends have been going on. What brands of potato chips were most popular this month? What other items did people who bought chips buy? That's just generic purchasing. When you use something like a store card that gives discounts they can get specific information about your buying habits.
This is a good thing.
If a store didn't stock its inventory according to the people in the community it wouldn't sell nearly as much as it could and would probably have to close. The people in the community would have to travel farther away to get the items they want, even if the store is operating. If the people in your community only like apples but the stores around you didn't carry apples everyone would suffer.
The Internet is more wild and untamed when it comes to information gathering than it should be. I don't think that such information gathering needs to be stopped, but it does need to be regulated a lot more than it is. People should be informed about when their information is being gather, even if they can't do anything to stop it. Unfortunately technology evolves faster than we do and any legislation that regulates online information gathering is going to have to be top notch, which means a long wait.