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 :)
When there's money and success at stake, it's difficult to be too cynical about what tactics are probably being employed.
Possible, but not much value for an arbitrage savvy publisher.
Not going to name names, but a good deal of fuckery is afoot in under article link exchange widgets. You know the ones, the boxes with link bait thumbnails that show up on a good deal of popular entertainment sites. Dealt with a lot of fake traffic coming through from the link exchange network. It appeared other publishers were sending tons of fake bot clicks to our site, in order to give themselves a higher amount of free reciprocal traffic from the link exchange.