What you describe is a system where the consumer has control over how they are advertised to, but that only works when you are the one with power in the situation. If you use a service for free, like a website, your eyeballs are the service being sold, and the advertiser is going to utilise that service in his interest. That includes putting ads you "don't like" in front of you, that actually do influence your chances of buying that product, on average, in an upward trend.