PPA and click fraud

Advertisers will like Pay per action adverts because they will pay out only when an action is completed. In the current experiment, advertisers can define what the action is (for example, a newsletter sign-up or a sale). It should eliminate the incidence of click fraud too, because the action has to complete before the advertiser has to pay Google. That's where things may start to become more complex.

If the desired action is a sale then at what point does the advertiser pay Google? At the point that their card acceptance service registers the payment from the customer? When the product or service is delivered? What happens if the advertiser pays Google for a completed sale and the customer subsequently asks for a full refund? If these issues can't be handled automatically, then Google may fall out of love with PPA very quickly.