I can't speak for today but in 2008-2010 this was definitely the case. It's not exactly a direct arbitrage play as a lot of the end advertisers tend to be doing

I can't speak for today but in 2008-2010 this was definitely the case. It's not exactly a direct arbitrage play as a lot of the end advertisers tend to be doing full media buys. Top banner ad, background page ads and they are just paying for 100% coverage for a day or week or month. One large gaming news/reviews site was buying about $10k/day worth of mostly fraudulent traffic. The traffic wasn't bots, per se, it was "real" users but they had compromised machines with popups and toolbars. So there was a high visit count of real users but there was no conversion metrics or time-on-site to be measured. They continued buying the traffic for at least a month so I can only assume it was meeting their goals. We had a lot of publishers all doing the same thing. As this was second tier, I wouldn't really call it "search" traffic. Just a ton of users with keyword-like queries being routed to various xml feeds/exchanges. When we'd send the traffic to actual publishers with conversion goals the rates were abysmal and we'd end up issuing lots of refunds. The only publishers that seemed to like the traffic were ones that sold their own dedicated ad units to large brand advertisers. I'm just glad to be out of that industry :)