I think that the op is talking about people embedding youtube videos, and they have ads on them. I never noticed them either but I don't care as much anymore.
, where are you seeing ads on here? And are you talking about youtube videos? Maybe you should check out adblocker, it actually works, and if you use it then you'll see because many sites out there will notice it and pop up a message saying how they need you to turn it off so they can make money. It's strange to me because people using it obviously aren't the traffic advertisers want because they don't care about the ads.