gregbo - 7:14 pm on Jun 29, 2006 (gmt 0)

i'm talking about the case in which a click has occured. whereas under ppc conditions the case is settled, under ppa conditions the time-span between click and action is vulnerable to numerous technical and behavioral distortions.

The case is not always settled in CPC. The SE/ad network can decline crediting the publisher if the click is considered invalid for some reason.

fraud is no less a problem under ppa. the difference is, that the threatening potential is now passed over to the advertiser side. if fraud is committed, it could be even more damaging for the whole reputation of the system because of the worse risk distribution for google and its affiliates.

Unless the vast majority of advertisers are fraudulent, the damage should only be limited to those fraudulent advertisers. An advertiser has an incentive not to cheat the system because access to the system improves their overall ability to do business.

my conclusion stands: cpc has shown to be the most convenient accounting method for all parties. in terms of risk distribution located right between cpm and cpa, it ensures the needed balance for financial planning aspects and assures, that none of the parties has to refuse the program to a greater extent.

Well, there are people who disagree.

the incredible popularity of adwords/adsense on both the advertiser and publisher side and the resulting huge financial success for google confirms that.

Not really. Money has changed hands; some people have profited; some people have been victimized by fraud.