May this be a complex illegal money transfer?

I have been watching Person of Interest in some websites. I recognized an issue with the ads in this website. The ads are just random videos. They advertise literally nothing. And, somebody is paying to this website for these ads. But why do they pay if the ad does not advertise something? That smells illegal to me. Imagine, you need to make a payment to someone. Let’s say that you are going to pay for a big pile of drug or gun or whatever other illegal trading item. Well, you can’t just write a bill as "drugs: 100k $". You have to make your payment in another way, in a "legal"…