If the fraud were evenly spread out, and if all advertisers had the same goal, the equilibrium bid just adjusts for less valuable clicks/interaction/etc (in line with what the earlier commenter mentioned), and the advertisers pay the same amount as in a world without fraud. Fraud isn't evenly spread out though, and advertisers are sometimes unaware, so it probably does hurt them.
The other loss is from honest publishers (think newspaper websites, etc.) - they're having to split payments with fraudsters, even though they're providing all the value to the advertiser. Downstream effects mean the publisher is probably producing less, showing more ads, or using other ways to replace ad income.
If the fraud were evenly spread out, and if all advertisers had the same goal, the equilibrium bid just adjusts for less valuable clicks/interaction/etc (in line with what the earlier commenter mentioned), and the advertisers pay the same amount as in a world without fraud. Fraud isn't evenly spread out though, and advertisers are sometimes unaware, so it probably does hurt them.
The other loss is from honest publishers (think newspaper websites, etc.) - they're having to split payments with fraudsters, even though they're providing all the value to the advertiser. Downstream effects mean the publisher is probably producing less, showing more ads, or using other ways to replace ad income.