The "seedier" actors in the ad space have always been about arbitrage. You can argue all you want how they're destroying the web, but the fact is they can purchase cheap traffic and remonetize it for gain. That's the definition of arbitrage and it exists in all types of industries, and is usually not viewed negatively.

Advertisers are in full control of assigning value to a traffic source by way of demographic targeting and bidding... Either the Advertisers are still profiting over the whole interaction or they're bidding too much for their traffic. It's not the middle men who are to blame.