let's not forget the positive side effect for all surfers: advertisers being able to monetize a website means more useful content for the web, that is more information and better surfing experience for the user. ok, in the worst case, if fraudsters and spammers are also able to monetize, that means more crap. one could blame google for indirectly promote both forms.
question is rather, to which party the business risk in terms of failure probability is transferred to. advertiser or publisher.
so, naturally advertisers prefer pay per lead/sale and publishers prefer pay per click/impression.
right, that's at the nature of things. easy to implement, easy to manipulate.
the user has to click on the ad, leave the browser open, make an immediate purchase and all that in one process to attribute the sale to the publisher. whereas most of the time, the advertiser gets free branding on the publishers' website. that is completely crazy. pay per sale as business model is at least as poor as cpc. so there's a draw.
i agree. interestingly, that would lead us back to some kind of cpm just like in traditional media.