Fraud is rampant. Also not new, although it is also also pretty easy to spot and block.
Almost nobody pays per 'impression' because, well that went out of style about the same time Yahoo! banner ads did.
Eventually the advertisers are going to pay for performance, and to do that they are going to have to fix the way they do advertising so that their ad, leads to their landing page which identifies who delivered the ad. Then they are going to pay based on whether or not the person who landed on their page actually buys something (service, good, or subscription). No money, no ad payment.
Most companies other than Amazon really aren't set up for that, and Amazon won't do it yet because, as far as I can tell, they aren't being forced too.
Its a shame that "affiliate" ads like the ones they let bloggers use have 100X there ROI of "CPC" ads and yet they have convinced the bloggers they can pay then a nickel and they should be happy when Google gets $13 - $23 for the same result.
I started building this system out of disgust but never finished it. It isn't that technically difficult, but it does have a lot of moving parts, and it does require infrastructure on the advertisers web site which can create durable transaction records. Some day I think.