Also the incentives of this setup are pretty screwed up. The advertising agency gets money as long as they are able to convince the advertiser that their services are worth it. But how do you really measure that? Sure, we have lots of fancy tracking technology, but not all consumers click ads to buy stuff. Whats the role of those purchases? Who knows. The agency will undoubtedly claim that all the sales were a direct result of an advertising company, and they have every incentive to say that. Do they really have any incentive to be completely honest about the effectiveness of their ads. I doubt it.