gregbo - 8:14 pm on Jun 24, 2006 (gmt 0)

Actually AdSense is ticking along quite successfully, so you could easily argue that the current model is very acceptable to advertisers.

I said nothing about the absolute success of AdSense; I discussed how CPA is less risky than CPC or CPM. Given initial advertiser reactions to CPA, I'd say that there is some feeling that it is preferable to CPC or CPM. So these advertisers will have the choice to move to CPA. The future, of course, will depend on whether CPA becomes sucessful enough that a majority of advertisers switch to it.