After a few months of private beta testing, Google has opened up its PayPerAction platform as a part of Adwords.

There will be a great deal of coverage and debate about the effectiveness of the program in the short term, but the real analysis is only going to be available after the system has been put through the test in the coming months. Then, we’ll see how the metrics work out.

There’s already a few good insights via TechMeme.

Google announced today the worldwide expansion of its pay-per-action advertising beta. Pay-per-action is a new pricing model that allows advertisers to pay only when a pre-defined action is completed on their site, such as when a user makes a purchase, signs up for a newsletter, or completes any other clearly defined action. Since the initial launch of the pay-per-action advertising beta in March 2007, many advertisers who have used the new pricing model are pleased with the opportunity to have more ways to promote their products and services online….

With this new pricing model, both advertisers and publishers gain more precision and control over their efforts to effectively spend advertising budgets and deliver relevant ads to related website content. Pay-per-action advertising is now available to qualifying advertisers worldwide.

All sorts of issues can be raised, and I’m sure this will be a hot topic at next month’s Affiliate Summit in Miami (especially with Google’s Rob Kniaz speaking on the 2nd Day’s Keynote). How will this affect the affiliate networks? Will advertisers demand more transparency than what is currently available (what sites will ads show up)? How does this back out to a CPC metric?

Google Press Center: News Announcement

[Update: Carsten Cumbrowski has the best review of this that I've read over at Search Engine Journal]