Don Dodge has a wrapup of Google's new Pay Per Action advertising plan. Under this model, advertisers only pay when users actually do something on the site, like filling out a form, providing email, etc. It's a natural step in targeting advertising.

PPA will be attractive to the highest cost CPC advertisers. My guess is that the very top of the CPC market will gravitate to PPA ads. Mortgage loan companies and automobile advertisers now pay the highest CPC rates, sometime $4 to $10 per click. These are very expensive clicks to get someone to read your ad. Why not filter out the curious ad clickers and just pay for the serious ones that actually fill out a form? These advertisers might be happy to pay $40 for a PPA that fills out a form. Multiply this by the millions of people every day looking for a loan or new car and you can see why this will be a very big business.

Spammers and Click Fraudsters will attack. Wherever there is money fraudsters are soon to follow. They will figure out ingenious ways to trick people into taking actions so they can collect the PPA revenues. The Spammers "cat and mouse" game has also just been taken to another level. There will need to be systems in place to verify the data entered into a form to make sure it is a valid action. They will need to verify that email addresses are valid or IP addresses for downloads are legitimate. You wouldn't believe how sophisticated these on-line fraudsters can be.

Arrington says:

Affiliate marketing networks like Commission Junction and LinkShare are screwed. These networks also operate on a cost-per-action basis, mostly with online retailers. Even though some of them have scale, they will not have the ability to compete with Google on sheer size of network. Advertisers flock to volume, which drives average pricing up. When prices increase, publishers flock to the new platform because they’ll earn more. Look for serious publisher leakage from the big affiliate networks over time as this new product scales up. If you want to argue this point, note what happened to the stock price of Commission Junction’s parent company, ValueClick, today. And that’s even though the market has largely adjusted for this news already - this move to add PPA ads has been rumored for some time.