cpc revolutionized the market, because it offered an accepable distribution of risk for all participiants.
It seems the risk was not acceptable to enough advertisers.
fraud is a problem. fraud can be managed if the rules are policed.
If you have any suggestions on how to reduce click fraud that haven't already been tried, please let's hear them.
the real problem that lies behind it is the distribution of risk, which with ppc was rather in balance for all involved and becomes insustainable for the publisher under a ppa environment.
If the distribution of risk was considered acceptable to advertisers, G would not have felt it necessary to offer PPA.
let's see if publishers (especially those with successful quality websites) are still ready to offer their advertising real estate under the new circumstances. you know every party in this game is dependent on the other side eventually.
I don't think G is as dependent on publisher revenue as you say. They have lots of ways to bring in revenue. If publishers won't allow PPA ads on their sites, I suspect it will not cause sufficient duress to G's bottom line that they drop the PPA program.