Determine a “toy” to research. A camera, a sweet new fishing pole, a type of car… whatever.. do about 20 minutes of window shopping on One or more commercial sites, and at least one price search engine.
Then watch the normal sites you visit that have the banner ads.
Notice as the ads become focused on the “toys” you have been looking at. They will constantly remind you of how badly you wanted those cool new gadgets. Even on sites that aren’t related to the content of the ads.
In fact look at the banner ad on the side bar.. (It has been showing me a really cool 20+ megapixel camera I looked at once.. over and over..)
What do YOU see?