Does search arbitrage hurt advertisers?
It can, and it can also help. Good arbitrage delivers extra interested visitors at a discounted click price. Poor arbitrage delivers people who were misled or have no intent to buy, and fraud delivers no people at all. Advertisers who never check partner performance carry the most risk; those who measure and exclude can keep the useful part.
Search engines argue that smart pricing and invalid-click filtering protect advertisers automatically. Critics, including some measurement firms, argue that partner inventory is opaque and that weak traffic still costs money. Both points have force, which is why Google added reporting and exclusions and withdrew parked domains by default.
The advertiser's practical tools are measurement and control: track conversions properly, segment by network, check lead quality, and use a placement exclusion or the advertiser opt-out where results are poor. Advertisers buying at scale often add third-party click verification; ClearTrust's ClickTrust is one product of that kind. Healthy arbitrage depends on advertisers getting value, so their scrutiny ultimately improves the market.