Let's say that became a reality, that most ads were served from the site of interest. Wouldn't the site's back end just send data about the client viewing an a

Let's say that became a reality, that most ads were served from the site of interest. Wouldn't the site's back end just send data about the client viewing an ad back to the ad vendor? I would think it would be part of their contract. I also have no problem with ads per se, but they aren't just ads anymore, ...