The likes of Commission Junction and TradeDoubler should be stirring their tea nervously, with news that Google is moving into the world of affiliate marketing. The AdSense blog reveals that they are now ‘accepting applications for new referrals beta’, leading to a flood of chatter in the blogosphere .

Cost-per-click advertising has been one of the great success stories of online advertising and has fueled the Google Advertising juggernaut. It’s strikes a satisfactory balance between the advertiser’s desire to pay for actions only and the publisher’s desire to get paid for branding. It has its critics with regards to ongoing problems with click fraud, but it continues to thrive because it works.

While the move into cost-per-action won’t threaten the cost-per-click cash cow anytime soon, it’s an interesting play to control yet more of the world’s online ad inventory.

It does make it harder to conduct click fraud (although the fraudsters will try), but will the returns be big enough for publishers to gain sufficient take-up? The beta is US only at present, so I will have to read about other’s findings to see if the numbers look likely to add up. I’m not so sure they will.